What is the recommended anaesthetic management and surgical approach for patients with hypertrophic obstructive cardiomyopathy (HOCM)?

Anaesthetic Management and Surgery for Hypertrophic Obstructive Cardiomyopathy

For patients with hypertrophic obstructive cardiomyopathy (HOCM) undergoing surgery, anesthetic management must strictly avoid factors that aggravate dynamic outflow obstruction such as positive inotropes, tachycardia, and reduced preload, while maintaining adequate afterload to reduce the risk of hemodynamic instability. 1

Pathophysiology Considerations

• HOCM is characterized by asymmetric hypertrophy of the interventricular septum causing intermittent obstruction of the left ventricular outflow tract (LVOT) 2
• Dynamic LVOT obstruction can be exacerbated by decreased preload, decreased afterload, or increased contractility 1
• Patients with HOCM may be asymptomatic at rest but can decompensate during anesthesia, leading to heart failure, myocardial ischemia, arrhythmias, or sudden cardiac death 1

Preoperative Assessment

• Evaluate severity of LVOT obstruction via echocardiography (resting and provoked gradients) 1, 3
• Continue beta-blockers and/or non-dihydropyridine calcium channel blockers without interruption in the perioperative period 1
• Discontinue vasodilators (ACE inhibitors, ARBs, dihydropyridine calcium channel blockers) and digoxin as they may worsen LVOT obstruction 1
• Avoid verapamil in patients with severe dyspnea at rest, hypotension, very high resting gradients (>100 mm Hg), and in children <6 weeks of age 1

Intraoperative Management

Hemodynamic Goals

• Maintain adequate preload (avoid hypovolemia) 1
• Maintain adequate afterload (avoid vasodilation) 1
• Avoid tachycardia to ensure adequate left ventricular filling 1
• Avoid positive inotropic agents that increase contractility 1
• Maintain sinus rhythm due to the prevalence of LV hypertrophy and decreased LV compliance 1

Monitoring

• Consider invasive arterial blood pressure monitoring 1
• Consider central venous pressure monitoring 1
• Consider intraoperative transesophageal echocardiography (TEE), especially in cases of hemodynamic instability to evaluate for LVOT obstruction 1, 3

Anesthetic Technique

• General anesthesia with careful titration of anesthetic agents to maintain hemodynamic stability 4, 2
• For non-cardiac surgery, early-extubation anesthesia (EEA) with low-dose fentanyl (10-15 μg/kg), propofol, midazolam, and inhalation agent has been shown to facilitate earlier extubation without increasing perioperative cardiac morbidity 4
• Neuraxial techniques can be used but require careful titration to avoid sudden decreases in afterload 5

Management of Hypotension

• If hypotension develops, prioritize intravenous fluid administration to correct hypovolemia 1
• Use alpha-agonists such as phenylephrine or vasopressin rather than beta-agonists, which can worsen LVOT obstruction 1
• In selected cases, intravenous beta-blockade may be necessary to reduce LV myocardial contractility and relieve LVOT obstruction 1

Surgical Management for HOCM

Indications for Septal Reduction Therapy (SRT)

• Severe symptoms despite optimal medical therapy 1
• Dynamic LVOT gradient ≥50 mm Hg at rest or with physiologic provocation 1
• Septal hypertrophy with systolic anterior motion (SAM) of mitral valve 1

Surgical Options

1. Surgical Myectomy (preferred for most patients) 1

   • Creates a rectangular trough in the basal septum below the aortic valve
   • More appropriate for younger patients, greater septal thickness, and concomitant cardiac disease
   • Preferred for patients with anomalous papillary muscles, elongated mitral leaflets, or intrinsic mitral valve disease

2. Alcohol Septal Ablation 1

   • Recommended for patients in whom surgery is contraindicated or high-risk due to comorbidities or advanced age
   • Less effective with gradients ≥100 mm Hg and septal thickness ≥30 mm
   • Higher risk of permanent pacemaker requirement and need for repeat intervention

Postoperative Care

• Continue beta-blockers and calcium channel blockers 1
• Monitor for conduction abnormalities (high requirement for temporary pacing) 4, 6
• Watch for atrial arrhythmias (occur in 25-34% of patients) 4
• Use cautious, low-dose diuretics only if signs of congestion are present 1
• Avoid positive inotropes and vasodilators 1

Common Pitfalls and Caveats

• Never use positive inotropes (dobutamine, dopamine, milrinone) as they worsen LVOT obstruction 1
• Avoid hypovolemia through careful fluid management 1
• Avoid vasodilators that reduce afterload and worsen obstruction 1
• Maintain sinus rhythm as loss of atrial contraction can significantly reduce cardiac output 1
• Treat hypotension with fluids and alpha-agonists, not beta-agonists 1
• Avoid aggressive diuresis as decreased preload can augment LVOT obstruction 1