What is the approach to using anticoagulants in patients with Hypertrophic Obstructive Cardiomyopathy (HOCM)?

Anticoagulation in Hypertrophic Obstructive Cardiomyopathy (HOCM)

All patients with HOCM who develop atrial fibrillation require lifelong anticoagulation with direct-acting oral anticoagulants (DOACs) as first-line therapy, regardless of their CHA₂DS₂-VASc score. 1

Primary Indication: Atrial Fibrillation

The presence of atrial fibrillation is the primary indication for anticoagulation in HOCM patients, as this population faces exceptionally high thromboembolic risk that is independent of traditional stroke risk stratification tools. 1

Clinical AF (Symptomatic Episodes)

• Initiate anticoagulation immediately with DOACs as first-line option 1
• Vitamin K antagonists (warfarin, target INR 2.0-3.0) serve as second-line option 1
• Traditional CHA₂DS₂-VASc scoring does not apply to HCM patients and should not guide anticoagulation decisions 1

Subclinical AF (Device-Detected)

The duration of AF episodes determines anticoagulation strategy:

• ≥24 hours duration: Anticoagulation is mandatory with DOACs first-line, warfarin second-line 1
• 5 minutes to <24 hours duration: Anticoagulation can be beneficial, considering total AF burden, episode duration, underlying risk factors, and bleeding risk 1
• Even a single short episode warrants strong consideration for lifelong anticoagulation given the catastrophic nature of stroke in this population 1, 2

DOAC vs. Warfarin: The Evidence

DOACs are preferred over warfarin based on superior mortality outcomes and comparable safety. The most recent guidelines prioritize DOACs as first-line therapy, supported by observational data showing:

• Lower all-cause mortality with DOACs compared to warfarin (HR 0.43-0.64) 3, 4
• Comparable thromboembolic event rates between DOACs and warfarin 3, 4
• Similar or lower major bleeding risk with DOACs 3, 4
• Lower composite fatal cardiovascular events with DOACs (HR 0.39) 4

The 2024 AHA/ACC guidelines represent the most current evidence, explicitly recommending DOACs as first-line over the 2014 ESC guidelines that recommended only vitamin K antagonists. 1 This shift reflects accumulating observational evidence demonstrating DOAC safety and effectiveness in HCM populations. 5, 3, 4

Critical Clinical Pitfalls

Do Not Use CHA₂DS₂-VASc Score

HCM patients are younger than typical AF populations and have inherently high stroke risk that is not captured by conventional scoring systems. 1 The stroke risk in HCM with AF is elevated regardless of age or other traditional risk factors. 6

Lifelong Therapy is Required

Anticoagulation must continue even after successful cardioversion or restoration of sinus rhythm, as AF recurrence rates are high and even brief episodes carry substantial thromboembolic risk. 1, 2

Atrial Flutter Requires Same Approach

Treat atrial flutter identically to atrial fibrillation regarding anticoagulation decisions. 1

Patients Without Atrial Fibrillation

Anticoagulation is not routinely indicated in HOCM patients without atrial fibrillation. 1 The primary indication for anticoagulation in this population is the presence of AF, not the cardiomyopathy itself. While HCM patients face elevated thromboembolic risk even without AF, current guidelines do not support prophylactic anticoagulation in sinus rhythm. 6

Rate Control Strategy

When initiating anticoagulation for AF, concurrent rate control is essential:

• Beta-blockers (preferred in most patients) 1
• Verapamil or diltiazem (non-dihydropyridine calcium channel blockers) as alternatives 1
• Choice depends on patient preferences, comorbidities, and presence of left ventricular outflow tract obstruction 1
• Target resting heart rate <100 bpm, with adequacy assessed during exercise 1

Never combine beta-blockers with verapamil or diltiazem due to risk of high-grade AV block. 7

Contraindications to Anticoagulation

For patients unable or unwilling to take oral anticoagulants, dual antiplatelet therapy with aspirin 75-100 mg plus clopidogrel 75 mg daily should be considered, though this is significantly inferior to anticoagulation. 1 Left atrial appendage occlusion devices remain untested in HCM populations and cannot be routinely recommended. 1