What is the management approach for a bifid pulse in a patient with Hypertrophic Obstructive Cardiomyopathy (HOCM)?

Management of Bifid Pulse in Hypertrophic Obstructive Cardiomyopathy (HOCM)

A bifid pulse in HOCM is a physical finding that indicates significant left ventricular outflow tract obstruction (LVOTO) requiring aggressive management with beta blockers, calcium channel blockers, or advanced therapies like cardiac myosin inhibitors, disopyramide, or septal reduction therapy based on symptom severity.

Understanding Bifid Pulse in HOCM

A bifid (or bisferiens) pulse is characterized by two distinct systolic peaks separated by a mid-systolic dip. In HOCM, this finding represents:

• Dynamic obstruction of the left ventricular outflow tract
• Systolic anterior motion (SAM) of the mitral valve causing mid-systolic partial obstruction
• The pulse pattern reflects the hemodynamic consequences of dynamic LVOTO

The bifid pulse is typically more pronounced with maneuvers that decrease preload or increase contractility, consistent with the dynamic nature of obstruction in HOCM.

Assessment of Patients with Bifid Pulse in HOCM

When a bifid pulse is detected in a patient with HOCM, the following should be evaluated:

• Severity of LVOTO (gradients ≥50 mmHg are generally considered capable of causing symptoms) 1
• Associated symptoms (dyspnea, chest pain, syncope)
• Presence of mitral regurgitation (often accompanies significant LVOTO)
• Diastolic dysfunction (commonly coexists)

Management Algorithm

First-Line Therapy

1. Non-vasodilating beta blockers

   • First-line therapy for symptomatic LVOTO
   • Titrate to effective dose with evidence of physiologic beta blockade (reduced heart rate)
   • Target: symptom improvement

2. Non-dihydropyridine calcium channel blockers (alternative first-line)

   • Verapamil or diltiazem
   • CAUTION: Verapamil is potentially harmful in patients with severe LVOTO (gradients >100 mmHg), hypotension, or severe dyspnea at rest 2

3. Eliminate medications that worsen LVOTO:

   • Dihydropyridine calcium channel blockers
   • ACE inhibitors/ARBs
   • Vasodilators
   • High-dose diuretics

Advanced Therapy for Persistent Symptoms

If symptoms persist despite optimal first-line therapy, proceed to one of the following 1:

1. Cardiac myosin inhibitors (for adults only)

   • Mavacamten has shown improvement in LVOT gradients and symptoms
   • Requires monitoring due to risk of decreased LVEF (<50%) in 5.7-10% of patients
   • Contraindicated in pregnancy due to teratogenic effects

2. Disopyramide

   • Must be used in combination with AV nodal blocking agent (beta blocker or calcium channel blocker)
   • Effective for symptom relief in patients failing first-line therapy

3. Septal reduction therapy (at experienced centers)

   • Surgical myectomy: >90% relief of obstruction with <1% mortality at experienced centers 3
   • Alcohol septal ablation: less invasive alternative with comparable results in selected patients 4
   • Choice between procedures depends on patient factors and institutional expertise

Management of Acute Hypotension

For patients with HOCM and bifid pulse who develop acute hypotension:

1. Maximize preload and afterload
2. Administer intravenous vasoconstrictors (phenylephrine)
3. Consider beta-blockade in combination with vasoconstrictors
4. Avoid inotropes that increase contractility (isoproterenol, dobutamine)

Special Considerations

• Atrial fibrillation: Common in HOCM and poorly tolerated due to loss of atrial contribution to ventricular filling

  • Anticoagulation is recommended regardless of CHA₂DS₂-VASc score 1
  • Rate control with beta blockers or non-dihydropyridine calcium channel blockers
  • Rhythm control with amiodarone, disopyramide, sotalol, or dofetilide as appropriate

• Monitoring: Regular assessment of LVOT gradient with echocardiography is essential to evaluate treatment response

Pitfalls to Avoid

1. Using vasodilators: Can worsen LVOTO and exacerbate symptoms
2. Using dobutamine for provocative testing: Lacks specificity and not recommended 1
3. Inadequate beta blockade: Failure of beta blockade should not be declared until physiologic evidence of beta blockade is observed
4. Underestimating stroke risk: Even paroxysmal AF in HOCM warrants anticoagulation
5. Using verapamil in severe LVOTO: Can cause dangerous hypotension in patients with high gradients (>100 mmHg) 2

By addressing the bifid pulse and underlying LVOTO in HOCM with appropriate medical and, if necessary, interventional approaches, symptoms can be effectively managed and long-term outcomes improved.