Anesthesia for patients with hypertrophic cardiomyopathy undergoing noncardiac surgery

INTRODUCTION — Hypertrophic cardiomyopathy (HCM) is a relatively common autosomal dominant inherited cardiomyopathy with a prevalence estimated to be up to 1 in 200 in the general population [1,2]. The clinical presentation is variable in that patients may be completely asymptomatic or may have severe symptoms, such as dyspnea, fatigue, chest pain, syncope, or may present with sudden cardiac death due to sustained ventricular arrhythmias.

Patients with HCM typically have asymmetric or localized areas of left ventricular hypertrophy (LVH) >15 mm without another identifiable cause (figure 1) [3-5]. Left ventricular outflow tract (LVOT) obstruction is present at rest or with provocation in the majority of patients due to systolic anterior motion (SAM) of the mitral valve with mitral-ventricular septal contact. In addition, SAM results in mitral regurgitation (MR) that is typically mild to moderate and usually posteriorly directed.

This topic will discuss anesthetic management during noncardiac surgery for patients with a preoperative diagnosis of HCM. The management strategies presented are also applicable to patients with previously undiagnosed HCM who develop perioperative hemodynamic instability and are found to have dynamic LVOT obstruction based on intraoperative rescue transesophageal echocardiography (TEE) [6,7]. (See "Intraoperative rescue transesophageal echocardiography (TEE)", section on 'Left ventricular outflow tract obstruction'.)

Medical and surgical management strategies for patients with HCM are reviewed in separate topics:

●(See "Hypertrophic cardiomyopathy: Management of patients without outflow tract obstruction".)

●(See "Hypertrophic cardiomyopathy: Management of patients with outflow tract obstruction".)

●(See "Hypertrophic cardiomyopathy: Management of ventricular arrhythmias and sudden cardiac death risk".)

PREANESTHETIC CONSULTATION — The preanesthetic consultation for patients with HCM is focused on decreasing risks for dynamic left ventricular outflow tract (LVOT) obstruction, minimizing microvascular ischemia, avoiding arrhythmias, and managing chronically administered medications [8-12].

It is prudent to obtain a cardiology consultation prior to elective surgery particularly for patients who are symptomatic (ie, New York Heart Association [NYHA] functional class II or greater) on medical therapy, and those with previously documented LVOT gradients ≥50 mmHg, to characterize the magnitude of current rest and latent LVOT gradients as well as the severity of mitral regurgitation (MR). In such cases additional testing or treatment may be necessary to minimize perioperative risk prior to considering elective non-cardiac surgery [13]. Selected patients may be candidates for invasive septal reduction therapies such as alcohol septal ablation or surgical septal myectomy [13-24]. (See "Hypertrophic cardiomyopathy: Management of patients with outflow tract obstruction".)

Review of clinically significant manifestations — The NYHA functional classification and the patient's history of arrhythmias, syncope, or angina, as well as personal or family history of sudden death, are noted. Key clinical features of HCM are variable but may include the following [8,25,26]:

●LVOT obstruction may be observed with transesophageal or transthoracic echocardiography when the LVOT is narrowed by marked left ventricular (LV) basal septal hypertrophy and/or abnormal length and positioning of the mitral valve leaflets resulting in systolic anterior motion (SAM) of the anterior mitral leaflet with ventricular septal contact (image 1). SAM septal contact creates a mechanical impedance of blood out of the LV producing a pressure gradient between the LV and the aorta, which can be accurately measured using the echocardiographic continuous wave Doppler method. Factors that increase this LVOT obstruction may precipitate acute hemodynamic collapse. Two-thirds of HCM patients have LVOT obstruction either at rest or with provocation, while the remainder have nonobstructive anatomy [14]. (See 'Hemodynamic goals and management' below and "Hypertrophic cardiomyopathy: Morphologic variants and the pathophysiology of left ventricular outflow tract obstruction", section on 'Dynamic nature of LVOT obstruction'.)

●SAM of the mitral valve also results in moderate to sometimes severe posteriorly directed MR due to inadequate coaptation of the mitral valve leaflets (movie 1) [27]. (See "Hypertrophic cardiomyopathy: Morphologic variants and the pathophysiology of left ventricular outflow tract obstruction", section on 'Development of mitral regurgitation'.)

●A small subset of HCM patients, with or without LVOT obstruction, may have associated severe pulmonary hypertension most often due to long-standing left-sided heart disease. Severe pulmonary hypertension can increase surgical risk in some cases; therefore, every effort should be made to identify this preoperatively.

●Ventricular arrhythmias may occur in patients with HCM [26]. These arrhythmias may cause syncope, and place patients at an increased risk for sudden cardiac death in the perioperative period and in other settings [28]. Patients are also at risk for supraventricular arrhythmias including atrial fibrillation, and may be taking anticoagulant prophylaxis to prevent stroke. (See "Hypertrophic cardiomyopathy in adults: Supraventricular tachycardias including atrial fibrillation" and "Hypertrophic cardiomyopathy: Risk stratification for sudden cardiac death".)

●Atypical chest pain occurs in 25 to 30 percent of patients with HCM [29,30]. Mechanisms include systolic and early diastolic compression of intramural vessels by the hypertrophied myocardium, which impairs microvascular coronary circulation causing subendocardial ischemia despite normal coronary angiography. Also, reductions in myocardial blood flow may occur due to small vessel disease with microvascular dysfunction, inadequate capillary density, myocardial fibrosis, and impaired vasodilator reserve [15-18,30-32]. Any exacerbation of LVOT obstruction and consequent decrease in blood pressure further impairs diastolic coronary blood flow to the hypertrophied myocardium. In addition, myocardial oxygen demand is increased in patients with HCM due to increased muscle mass, myocyte hypertrophy and disarray, and increased wall stress due to elevated LV diastolic pressures. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation", section on 'Chest pain'.)

●Diastolic LV dysfunction with impaired relaxation is common and is most commonly assessed by echocardiography (see "Echocardiographic evaluation of left ventricular diastolic function in adults"). When diastolic dysfunction is severe, it can cause advanced heart failure with a low-output state. (See "Hypertrophic cardiomyopathy: Natural history and prognosis", section on 'Nonobstructive with preserved systolic function (ejection fraction ≥50 percent)'.)

●LV systolic function is normal or hyperdynamic in the vast majority of HCM patients [8]. A very small subset of HCM patients (<5 percent) develop progressive and irreversible transmural replacement of myocardium with scar tissue resulting in systolic dysfunction and end-stage heart failure [19,26]. (See "Hypertrophic cardiomyopathy: Natural history and prognosis", section on 'HCM with LV systolic dysfunction (ejection fraction <50 percent)' and "Hypertrophic cardiomyopathy: Natural history and prognosis", section on 'Heart failure'.)

●HCM is distinguished from other causes of cardiac hypertrophy (eg, hypertension, aortic stenosis, athlete's heart), although these diagnoses can coexist with HCM in some patients. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation", section on 'Differential diagnosis'.)

Review of preoperative studies

●Cardiac studies

•Electrocardiogram – Obtain a preoperative electrocardiogram (ECG) and compare this with prior ECG tracings. The baseline ECG will be useful for comparison with postoperative ECG tracings that may be abnormal. (See "The preoperative ECG: Evaluation and implications for anesthetic management" and 'Postoperative anesthetic management' below.)

Most patients (90 percent) with HCM demonstrate ECG abnormalities, such as left ventricular hypertrophy (LVH), left atrial enlargement, T wave inversions, ST-segment depressions, or left anterior hemiblock [33]. Other abnormal findings include sinus tachycardia or other supraventricular or ventricular arrhythmias. If severe, such arrhythmias are managed with pharmacologic therapy or ablation prior to an elective surgical or other interventional procedure. While a normal ECG is generally associated with less severe disease, a normal ECG does not exclude severe disease [34]. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation", section on 'Electrocardiography'.)

•Echocardiogram – Review available transthoracic and/or transesophageal echocardiograms to assess the severity of LVH, LVOT gradient, systolic anterior motion (SAM) of the mitral valve, or other anomalies [13,35,36]. Patients may demonstrate LVOT obstruction at rest or with provocation. The presence of peak gradients of ≥30 mmHg (obtained by continuous wave doppler) indicates obstruction. Resting or provoked gradients ≥50 mmHg should prompt referral for septal reduction therapies (alcohol or surgical). Patients without obstruction at rest are at risk for development of dynamic (ie, provocable) LVOT obstruction and secondary MR during certain clinical scenarios (eg, vasodilation induced by anesthetic agents or tachycardia and increased contractility caused by sympathetic responses to surgical stimulation) (see 'Hemodynamic goals and management' below) [37-39]. Preoperative echocardiography may also provide estimates of systolic ejection fraction, severity of diastolic dysfunction, and pulmonary artery pressure. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation", section on 'Echocardiography'.)

•Cardiovascular magnetic resonance imaging (MRI) – Cardiovascular MRI studies may have been obtained if echocardiography was inconclusive in determining LV wall thickness, the pattern of hypertrophy, or anatomy of the mitral valve or subvalvular apparatus (eg, abnormal papillary muscles) [37]. Cardiovascular MRI can also provide information regarding right ventricular hypertrophy, diastolic function, regional wall motion, and sudden death risk stratification [5]. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation", section on 'Cardiovascular magnetic resonance'.)

•Cardiac catheterization with coronary angiography – LVOT gradients can be reliably obtained in nearly all HCM patients using a noninvasive approach with Doppler echocardiography. However, if the presence or magnitude of an LVOT gradient is uncertain after echocardiography, the cardiologist may perform left heart catheterization to obtain direct measurements of filling pressures and the LVOT gradient (ie, the difference in LV systolic pressures measured at sites distal and proximal to the obstruction within the LV cavity (waveform 1)). In addition, if obstructive coronary disease is suspected based on clinical history, coronary angiography is employed to assess for significant epicardial coronary artery disease [40]. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation", section on 'Coronary angiography'.)

●Other studies – Sleep apnea is present in >50 percent of patients with HCM [41,42]. Details regarding preoperative evaluation and management are discussed separately. (See "Surgical risk and the preoperative evaluation and management of adults with obstructive sleep apnea".)

Preoperative management — Important considerations include:

●Continuation of chronically administered beta blocking agents (atenolol, metoprolol, or propranolol) or nondihydropyridine calcium channel blocker (diltiazem or verapamil). These agents have negative inotropic and negative chronotropic properties. They beneficially reduce LVOT obstruction, decrease heart rate to prolong diastole and improve the myocardial oxygen supply-demand relationship, and reduce risk of arrhythmias [25,26,37,43]. Typically, a low to normal heart rate of approximately 60 beats per minute is desirable. (See "Hypertrophic cardiomyopathy: Management of patients without outflow tract obstruction".)

●Management of chronically administered anticoagulant agents (eg, direct acting oral anticoagulants [DOACS], vitamin K antagonists [4,44]) in patients with atrial fibrillation, with consideration of the balance between preventing excessive bleeding and reducing the risk of stroke [26,45,46]. Issues regarding timing of discontinuation of specific anticoagulants, bridging with administration of a short-acting agent, and resuming chronic anticoagulant therapy are discussed separately. (See "Perioperative management of patients receiving anticoagulants".)

●Management of a pacemaker or implantable cardioverter-defibrillator (ICD), with planning for reprogramming or applying a magnet to the device, as appropriate (algorithm 1). Patients with a history of cardiac arrest, ventricular fibrillation, sustained ventricular tachycardia, or considered at high risk for ventricular tachyarrhythmias typically have an ICD [3,25,26,37]. Some patients with HCM have a permanent pacemaker (eg, when required after septal reduction therapy). During surgery, pacemaker or ICD function may be affected by electromagnetic interference such as electrocautery, which can cause delivery of inappropriate shock(s) or inhibit needed anti-bradycardia pacing in a pacing-dependent patient. Thus, if electrocautery will be used for surgery performed superior to the umbilicus or near the pulse generator or leads of the ICD, it is necessary to reprogram the device to an asynchronous mode or apply a magnet in selected patients. Detailed discussion of perioperative ICD management is available in a separate topic. (See "Perioperative management of patients with a pacemaker or implantable cardioverter-defibrillator", section on 'Preoperative assessment'.)

HEMODYNAMIC GOALS AND MANAGEMENT — In patients with HCM, left ventricular outflow tract (LVOT) obstruction and secondary mitral regurgitation (MR) worsen with hypovolemia, vasodilation, tachycardia, and/or a high catecholamine state, potentially leading to severe hypotension and hemodynamic collapse [6]. Also, patients with HCM are susceptible to myocardial ischemia and supraventricular and ventricular tachyarrhythmias since any exacerbation of LVOT obstruction impairs diastolic coronary blood flow delivering oxygen to hypertrophied myocardium.

The following hemodynamic goals are important during perioperative management of a patient with HCM (table 1) (see "Hypertrophic cardiomyopathy: Management of patients with outflow tract obstruction", section on 'Acute shock'):

●Maintain euvolemia – Preload is maintained or increased, while hypovolemia should be avoided. Hypovolemia exacerbates LVOT obstruction and MR, potentially causing systemic hypotension and hemodynamic collapse. Patients undergoing emergency surgery are particularly vulnerable to development of hypovolemia since significant blood loss may have occurred, or there may be little time for volume resuscitation before anesthetic induction.

Hypovolemia is promptly treated with intravenous (IV) fluid boluses titrated according to clinical assessment of volume status and the patient's hemodynamic response. A goal-directed approach to fluid therapy is typically employed, with use of dynamic parameters to assess intravascular volume status and guide fluid administration. (See "Intraoperative fluid management", section on 'Dynamic parameters to assess volume responsiveness'.)

It is important to ensure adequate IV access to avoid hypovolemia (eg, large-bore IV access if significant blood or other volume losses are likely). Positional maneuvers such as placing the patient in Trendelenburg may be employed to augment preload temporarily.

●Maintain adequate systemic vascular resistance – Avoid afterload reduction (ie, decreased systemic vascular resistance [SVR]) as this will exacerbate LVOT obstruction and worsen MR in patients with HCM, leading to hypotension and possible hemodynamic collapse. Decreases in afterload are immediately treated with peripheral vasoconstrictor agents such as phenylephrine or vasopressin (table 2). These agents increase SVR and may also cause a reflex bradycardia, effects that lessen the degree of LVOT obstruction and also protect against myocardial ischemia. Of note, positive inotropic drugs such as epinephrine and ephedrine should not be used to increase systemic blood pressure because these agents increase contractility, which may further worsen LVOT obstruction and exacerbate hypotension.

●Maintain sinus rhythm – Maintenance of sinus rhythm to optimize left ventricular (LV) preload is particularly important since a large fraction of ventricular diastolic filling is supplied by the atrial contraction (atrial "kick") at end-diastole. The ability to externally cardiovert or defibrillate life-threatening arrhythmias is ensured by placing transcutaneous pacing/defibrillator pads on the patient prior to anesthetic induction, as well as ensuring immediate availability of a functioning cardioverter/defibrillator machine. (See "Perioperative management of patients with a pacemaker or implantable cardioverter-defibrillator", section on 'Placement of transcutaneous pacing/defibrillator pads'.)

Severe hypotension typically occurs if atrial fibrillation develops due to sudden loss of the atrial kick, which results in marked reduction in LV filling and stroke volume. The majority of HCM patients, with or without LVOT obstruction, are sensitive to hemodynamic and clinical deterioration during acute episodes of atrial fibrillation, even if the ventricular heart rate is not particularly rapid. Thus, new onset of atrial fibrillation or other supraventricular tachyarrhythmias is immediately treated to attempt to restore sinus rhythm, as well as to control the ventricular rate. Direct current cardioversion may be necessary if the patient is hemodynamically unstable with a rapid ventricular response. (See "Arrhythmias during anesthesia", section on 'Atrial tachyarrhythmias'.)

Similarly, sudden onset of atrioventricular dissociation (eg, a junctional rhythm) also results in a loss of the atrial kick and may cause severe hypotension. (See "Arrhythmias during anesthesia", section on 'Atrioventricular nodal reentrant tachycardia' and "Arrhythmias during anesthesia", section on 'First, second, or third degree AV block'.)

Normal electrolyte values should be maintained throughout the perioperative period to reduce the risk of atrial and ventricular arrhythmias.

Due to the markedly abnormal myocardial substrate in patients with HCM and the acute changes in hemodynamics in the perioperative setting, life-threatening ventricular arrhythmias requiring immediate cardioversion or defibrillation can occur, albeit rarely, even after surgery. (See 'Postoperative anesthetic management' below.)

●Maintain a low to normal heart rate – A heart rate of 60 to 80 beats per minute is optimal to minimize LVOT obstruction, optimize ventricular filling, and reduce the risk of ischemia (table 3). If necessary, small IV doses of a beta blocker (eg, esmolol 20 to 30 mg or metoprolol 2.5 to 5 mg) are administered to decrease heart rate.

In patients with pre-existing atrial fibrillation, the ventricular rate should be well-controlled to maintain the heart rate at 60 to 80 beats per minute. Continuing beta blockade throughout the perioperative period is essential.

●Avoid increases in contractility – Increases in LV contractility should be avoided since this exacerbates LVOT obstruction. Sympathetic stimulation caused by pain or other noxious stimuli is minimized by increasing anesthetic depth to avoid increases in contractility (eg, increasing concentration of a volatile agent or administering titrated doses of an opioid such as fentanyl 25 to 50 mcg). Small IV doses of a beta blocker (eg, esmolol 20 to 30 mg or metoprolol 2.5 to 5 mg) may also be administered to beneficially decrease contractility.

Inotropic agents are avoided unless patients have end-stage heart failure. Treatment of hypotension is accomplished by augmenting preload and use of peripheral vasoconstrictor agents such as phenylephrine or vasopressin, rather than by administering any agent with inotropic properties.

HEMODYNAMIC MONITORING — The need for invasive hemodynamic monitoring depends on patient-specific and surgery-specific factors that may increase risk for hemodynamic instability and/or arrhythmias.

●Intra-arterial catheter – We typically insert an intra-arterial catheter before induction of anesthesia if certain patient-specific or surgery-specific risk factors are present in patients with a known diagnosis of HCM.

•Patient factors include:

-New York Heart Association (NYHA) class III-IV heart failure

-History of clinically significant resting or dynamic left ventricular outflow tract (LVOT) obstruction producing a gradient ≥30 mmHg [37]

-History of rapid atrial fibrillation or ventricular arrhythmias

-Likely need for vasopressor infusion support

-Severe pulmonary hypertension

-Systolic ejection fraction <50 percent

•Surgical factors include procedures involving:

-Large changes in intravascular volume status that may lead to decreased preload, such as procedures likely to cause extensive blood loss or other intravascular volume shifts. Also, laparoscopic procedures may cause decreased preload due to increased intra-abdominal and intrathoracic pressures when carbon dioxide (CO₂) is insufflated [47].

-Planned volume expansion that may precipitate pulmonary edema in certain surgical procedures.

-Likely acute changes in afterload (eg, procedures requiring aortic clamping and unclamping).

-Electrolyte imbalances (such as those associated with reperfusion of transplanted organs) that may lead to arrhythmias.

-Emergency surgery, particularly in patients who are hemodynamically unstable or have suffered significant preoperative blood loss, or if there is little time for volume resuscitation before anesthetic induction [48].

The intra-arterial catheter is used for continuous monitoring of arterial blood pressure, as well as evaluation of respirophasic variations in the arterial pressure waveform (figure 2) [8]. Intermittent blood sampling is also possible to check arterial blood gases and pH, hemoglobin, and electrolytes. (See "Intraoperative fluid management", section on 'Dynamic parameters to assess volume responsiveness'.)

●Transesophageal echocardiography – The authors also employ transesophageal echocardiography (TEE) for surgical procedures in high-risk HCM patients who require intra-arterial catheter placement and are at risk for large changes in preload or afterload. Similarly, TEE is typically employed during transplantation procedures involving significant electrolyte and fluid shifts (eg, liver transplantation). Some clinicians use TEE during laparoscopic procedures to assess for development of systolic anterior motion (SAM) during insufflation of CO₂ [49]. (See "Intraoperative transesophageal echocardiography for noncardiac surgery".)

In addition, emergency use of perioperative TEE is indicated to determine the cause of unexplained persistent or life-threatening circulatory instability ("rescue echo"). TEE can rapidly identify LVOT obstruction, mitral regurgitation (MR), hypovolemia, and left or right ventricular dysfunction in patients with known or previously unrecognized HCM (image 1 and movie 1) [6,7,47]. (See "Intraoperative rescue transesophageal echocardiography (TEE)", section on 'Left ventricular outflow tract obstruction'.)

●Central venous catheter – A central venous catheter (CVC) may be indicated for the administration of vasopressors, or if large-bore peripheral venous access cannot be obtained. Central venous pressure (CVP) should be monitored to provide supplemental data regarding intravascular volume status if a CVC is inserted. However, CVP values poorly predict hypovolemia and fluid responsiveness, as discussed separately. (See "Intraoperative fluid management", section on 'Traditional static parameters'.)

CHOICE OF ANESTHETIC TECHNIQUE

Monitored anesthesia care — For patients with HCM undergoing minor procedures requiring only sedation with monitored anesthesia care (MAC), standard American Society of Anesthesiologists (ASA) monitoring is usually sufficient (table 4) [50]. (See "Monitored anesthesia care in adults", section on 'Monitoring during monitored anesthesia care'.)

Adequate analgesia may avoid sympathetic responses that result in tachycardia and increased contractility. Small doses of an opioid and/or a benzodiazepine are typically employed. Dexmedetomidine has also been used to sedate patients with HCM due to its beneficial effects, including lowering heart rate and blunting sympathetic responses to surgery. Propofol may be administered cautiously (ie, in small doses) to avoid its dose-dependent vasodilatory effects that can exacerbate left ventricular outflow tract (LVOT) obstruction. Ketamine is avoided due to its sympathomimetic properties that typically increase heart rate and contractility thereby exacerbating LVOT obstruction. (See "Monitored anesthesia care in adults", section on 'Drugs used for sedation and analgesia for monitored anesthesia care'.)

If necessary, a beta blocker (eg, esmolol 20 to 30 mg or metoprolol 2.5 to 5 mg) may be administered to control increased heart rate caused by pain or anxiety. In some cases, combining sedation with a peripheral nerve block can provide excellent analgesia while avoiding the decreases in systemic vascular resistance (SVR) that occur due to neuraxial or general anesthetic agents and techniques.

Neuraxial anesthesia — A neuraxial technique (eg, epidural, spinal, combined spinal-epidural) with local anesthetic induces a sympathectomy. A neuraxial technique may be used in a patient with HCM if the hemodynamic goals for managing such patients are kept in mind (table 1). For example, a very slowly titrated epidural anesthetic or a low-dose combined spinal-epidural may be selected for cesarean section in a parturient with HCM [8]. Benefits of epidural analgesia include avoidance of the sympathetic stimulation associated with the pain of uterine contractions during labor and delivery that can precipitate increased contractility, sinus tachycardia, or supraventricular or ventricular arrhythmias, effects that worsen LVOT obstruction and/or result in myocardial ischemia.

However, any decrease in SVR resulting from a neuraxial technique will exacerbate LVOT obstruction and may result in severe hypotension. To mitigate these effects, a phenylephrine or vasopressin infusion is typically administered to counterbalance the vasodilation expected from the neuraxial anesthetic (table 2). Rapid induction of profound sympathectomy (eg, a high spinal) is avoided. (See "Anesthesia for labor and delivery in high-risk heart disease: Specific lesions", section on 'Hypertrophic cardiomyopathy (HCM)'.)

An intra-arterial catheter for continuous blood pressure monitoring is typically inserted if a neuraxial anesthetic technique is selected so that hypotension may be recognized and promptly treated. (See 'Hemodynamic monitoring' above.)

General anesthesia — Preload and SVR are maintained or increased during maintenance, while sinus tachycardia, other arrhythmias, and increases in contractility are avoided, similar to management of general anesthesia for non-cardiac surgery in patients with aortic stenosis and fixed left ventricular (LV) obstruction. (See "Anesthesia for noncardiac surgery in patients with aortic or mitral valve disease", section on 'Aortic stenosis'.)

However, use of positive inotropes (eg, epinephrine) or anesthetic agents with sympathomimetic properties (eg, ketamine) are avoided. Administration of any agent that increases contractility causes worsening of the dynamic LVOT obstruction, thereby worsening hypotension in patients with HCM.

If hemodynamic instability with LVOT obstruction occurs, prompt treatment is necessary to avoid hemodynamic collapse. This includes (table 1) (see "Hypertrophic cardiomyopathy: Management of patients with outflow tract obstruction", section on 'Acute shock'):

●Increasing LV volume with fluid administration

●Increasing SVR with vasoconstrictors that do not have inotropic properties (eg, phenylephrine or vasopressin)

●Decreasing heart rate (to 60 to 80 beats per minute) and contractility with anesthetic or beta blocking agents

Induction — Induction agents and doses are selected to reduce the likelihood of hypotension, while establishing adequate anesthetic depth during laryngoscopy and endotracheal intubation to minimize sympathetic stimulation and avoid tachycardia and increased contractility. If propofol is selected, it is administered in an initial low dose of 0.5 to 1 mg/kg, then additional propofol may be titrated to effect. Adjunct induction agents such as an opioid (eg, fentanyl) or benzodiazepine (eg, midazolam) may be administered to decrease the total dose of propofol required to ensure amnesia and loss of consciousness. Also, vasopressors that increase SVR without increasing heart rate or contractility (eg, phenylephrine or vasopressin) may be administered prophylactically [8]. We avoid administration of a high initial dose of propofol (eg, >1.5 mg/kg) to avoid decreases in SVR. (See "General anesthesia: Intravenous induction agents", section on 'Propofol' and "General anesthesia: Intravenous induction agents", section on 'Adjuvant agents'.)

While etomidate has been used effectively for anesthetic induction in patients with HCM, the authors favor agents without a risk for transient acute adrenal insufficiency. (See "General anesthesia: Intravenous induction agents", section on 'Etomidate'.)

Ketamine is avoided due to its sympathomimetic stimulation that would cause unfavorable inotropic and chronotropic effects. (See "General anesthesia: Intravenous induction agents", section on 'Ketamine'.)

Maintenance — The potent volatile inhalation anesthetics desflurane, sevoflurane, and isoflurane are all vasodilators. While these agents cause beneficial reductions in myocardial contractility in patients with HCM, higher doses may cause excessive vasodilation, thereby obviating the salutary hemodynamic effects in these patients. An opioid may be administered to decrease the volatile anesthetic agent dose. (See "Inhalation anesthetic agents: Clinical effects and uses" and "Perioperative uses of intravenous opioids in adults: General considerations", section on 'Maintenance'.)

High doses of desflurane are avoided due to potential sympathomimetic effects which may cause tachycardia and increased contractility. Use of nitrous oxide, while not contraindicated, can further elevate pulmonary artery pressures, which may be abnormal at baseline in patients with HCM [9]. (See "Inhalation anesthetic agents: Clinical effects and uses", section on 'Desflurane' and "Inhalation anesthetic agents: Clinical effects and uses", section on 'Nitrous oxide'.)

As noted above, hemodynamic goals throughout the period of maintenance of anesthesia include (see 'Hemodynamic goals and management' above):

●Maintain or increase preload – Intravenous (IV) fluids are administered as needed. (See "Intraoperative fluid management".)

Positional maneuvers such as placing the patient in Trendelenburg can augment preload temporarily. During a laparoscopic surgical procedure with carbon dioxide (CO₂) insufflation, close communication with the surgical team is necessary to avoid hemodynamically significant decreases in preload, particularly if high insufflation pressures are employed. High tidal volumes and excessive positive end expiratory pressure (PEEP) are avoided as these may have deleterious effects on preload; thus, we typically maintain PEEP at 5 mmHg [51].

●Maintain systemic vascular resistance – Continuous infusion of a vasopressor (eg, phenylephrine or vasopressin) is often employed during the maintenance phase to prevent decreases in SVR. (See "Intraoperative use of vasoactive agents", section on 'Vasopressor and positive inotropic agents'.)

●Avoid increases in contractility and heart rate – Sympathetic stimulation that results in tachycardia and increased contractility can precipitate hemodynamic collapse. Increasing anesthetic depth or administering small doses of IV or neuraxial opioids can blunt sympathetic responses to pain and other noxious stimuli. Small IV doses of a beta blocker (eg, esmolol 20 to 30 mg or metoprolol 2.5 to 5 mg) may also be administered to beneficially decrease contractility.

Anesthetic and vasoactive agents that may increase heart rate or augment contractility are avoided.

Emergence — During emergence, tachycardia and increased contractility due to sympathetic stimulation caused by pain and agitation, as well as stimulation of airway reflexes during tracheal extubation, can lead to LVOT obstruction and myocardial ischemia in a patient with HCM. These hemodynamic changes are minimized by providing optimal analgesia prior to emergence (eg, by administering a systemic opioid or doses of local anesthetic via an existing epidural catheter) and/or by administering bolus doses of an IV beta blocker (eg, esmolol, metoprolol) during and immediately after emergence and extubation.

Hypothermia and shivering also lead to tachycardia and increased metabolic oxygen consumption with exacerbation of myocardial ischemia. Thus, normothermia should be maintained throughout the perioperative period. (See "Perioperative temperature management", section on 'Intraoperative hypothermia'.)

POSTOPERATIVE ANESTHETIC MANAGEMENT — Recovery after noncardiac surgery in patients with HCM is often managed in the post-anesthesia care unit (PACU). Admission to an intensive care unit (ICU) may be necessary for patients who have undergone major surgery with significant blood loss and for those with hemodynamic instability. In either recovery setting, early postoperative considerations include the following:

●If an implantable cardioverter-defibrillator device (ICD) was reprogrammed before surgery, it is critical to ensure reactivation of the original settings in the postoperative period before the patient leaves the PACU (algorithm 2) [12]. Until reactivation is accomplished, transcutaneous pacing/defibrillator pads should remain in place and the patient is continuously monitored with electrocardiography (ECG) telemetry to identify clinically relevant atrial or ventricular arrhythmias. Similarly, telemetry is prudent during the immediate postoperative period for patients with HCM who do not have an ICD in place. (See "Perioperative management of patients with a pacemaker or implantable cardioverter-defibrillator", section on 'Postoperative management'.)

●If large perioperative fluid shifts occurred, electrolytes are checked and abnormalities are corrected to prevent exacerbation of arrhythmias.

●If tolerated, resumption of beta or calcium channel blocking agents in the postoperative period is important in patients who were receiving chronic therapy, to maintain a slow to normal heart rate and possibly prevent or ameliorate myocardial ischemia.

●The surgical and cardiology teams are consulted regarding resumption of anticoagulation for atrial arrhythmias.

●Since there is increased risk for microvascular ischemia in patients with HCM, all patients with symptoms or ECG changes suggestive of ischemia or myocardial infarction should be monitored with troponin measurements and 12-lead ECG to detect myocardial injury [52,53]. Ideally, a baseline ECG will be available for comparison, since preoperative abnormalities are common in patients with HCM.

●Effective postoperative pain management is important to avoid pain-induced sympathetic stimulation leading to tachycardia and increases in contractility [51]. (See "Anesthesia for noncardiac surgery in patients with ischemic heart disease", section on 'Management of pain' and 'Hemodynamic goals and management' above.)

●Suspected fluid overload warrants assessment for possible pulmonary edema and the need for judicious use of diuretic therapy. Cardiac consultation is often necessary for patients with pre-existing heart failure and in patients who develop acute heart failure exacerbation in the perioperative period [10,48]. (See "Perioperative management of heart failure in patients undergoing noncardiac surgery", section on 'Postoperative management'.)

●If hypotension is present and/or if intravascular volume status is unclear, transthoracic or transesophageal echocardiography can be performed. (See 'Hemodynamic goals and management' above and "Hypertrophic cardiomyopathy: Morphologic variants and the pathophysiology of left ventricular outflow tract obstruction", section on 'Dynamic nature of LVOT obstruction'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Cardiomyopathy".)

SUMMARY AND RECOMMENDATIONS

●Review of clinical manifestations and studies – Hypertrophic cardiomyopathy (HCM) has morphologic variants (figure 1). Most HCM patients can develop dynamic left ventricular outflow tract (LVOT) obstruction due to systolic anterior motion (SAM) of the mitral valve with ventricular septal contact and associated mitral regurgitation (MR) that can cause acute hemodynamic instability (image 1). Other clinical manifestations of HCM may include microvascular myocardial ischemia, supraventricular and ventricular arrhythmias, diastolic dysfunction, and rarely systolic dysfunction with ejection fraction <50 percent. (See 'Review of clinically significant manifestations' above and 'Review of preoperative studies' above.)

●Preoperative management – Maintenance of stable blood pressure and intravascular volume during the perioperative period is important to decrease risk for development of dynamic LVOT obstruction and tachycardia (which impairs ventricular filling), as well as to minimize microvascular ischemia and avoid atrial and ventricular arrhythmias. Chronically administered beta blocking agents (atenolol, metoprolol, or propranolol) or nondihydropyridine calcium channel blocker (diltiazem or verapamil) are continued. Patients with an implantable cardioverter-defibrillator (ICD) may require reprogramming or magnet application to the device, as appropriate (algorithm 1). (See 'Preoperative management' above.)

●Hemodynamic goals and management – LVOT obstruction and MR worsen with hypovolemia, vasodilation, tachycardia, and/or a high catecholamine state in patients with HCM, and may result in severe hypotension or hemodynamic collapse. Thus, euvolemia, adequate systemic vascular resistance (SVR), and sinus rhythm at a slow to normal heart rate (HR) of 60 to 80 beats per minute should be the goal during the entire perioperative period, while increases in contractility or pulmonary vascular resistance (PVR) are avoided (table 1). (See 'Hemodynamic goals and management' above.)

●Hemodynamic monitoring – The need for invasive hemodynamic monitors (eg, intra-arterial catheter, transesophageal echocardiography [TEE], central venous catheter) depends on patient-specific factors such as symptomatic heart failure, LVOT gradient ≥30 mmHg, ejection fraction <50 percent, severe pulmonary hypertension, or history of rapid atrial or ventricular arrhythmias, as well as surgery-specific factors that increase risk of hypovolemia, hemodynamic instability, and/or arrhythmias. Examples include anticipated bleeding or other large shifts in intravascular volume, acute changes in afterload, or emergency surgery with hemodynamic instability. (See 'Hemodynamic monitoring' above.)

●Anesthetic management

•Monitored anesthesia care – For minor procedures, sedation with noninvasive monitoring and monitored anesthesia care (MAC) is usually sufficient. (See 'Monitored anesthesia care' above.)

•Neuraxial anesthesia – In selected patients, a very slowly titrated epidural anesthetic or a low-dose combined spinal-epidural may be employed (eg, a parturient undergoing cesarean section). However, sympathectomy caused by neuraxial blockade decreases SVR and may exacerbate LVOT obstruction, worsen MR, and result in severe hypotension. To mitigate these effects, a phenylephrine or vasopressin infusion may be administered to counterbalance the vasodilation expected from the neuraxial anesthetic. (See 'Neuraxial anesthesia' above.)

•General anesthesia – Intraoperative management of general anesthesia involves maintenance of preload and SVR and avoidance of tachycardia and increases in contractility throughout the perioperative period. If hemodynamic instability with LVOT obstruction occurs, immediate treatment includes (table 1) (see 'General anesthesia' above):

-Increasing left ventricular (LV) volume with fluid administration

-Increasing SVR with vasoconstrictors that do not have inotropic properties (eg, phenylephrine or vasopressin)

-Decreasing HR to 60 to 80 beats per minute and decreasing contractility with anesthetic or beta blocking agents

●Postoperative considerations – In the postoperative period, management includes effective pain relief to avoid pain-induced sympathetic stimulation leading to tachycardia and increases in contractility, management of a reprogrammed ICD (algorithm 2), and resumption of medications such as beta or calcium channel blocking agents. Assessment with echocardiography is prudent for patients with hypotension or if intravascular volume status (eg, hypovolemia or hypervolemia) is unclear. (See 'Postoperative anesthetic management' above.)