Hypertrophic Cardiomyopathy Part 2: Workup and Treatment

Co-authors: Taylor Murtaugh MD, Esteban Davila MD

We're back after a short hiatus for part 2. You can find part 1 here.

The Case Continued

History and Physical

When suspecting hypertrophic cardiomyopathy (HCM), the history should focus on overall fitness as well as adverse responses to exertion such as chest pain, shortness of breath, palpitations, and syncope. Symptoms of left ventricular outflow tract obstruction (LVOTO) commonly include exertional dyspnea, fatigue with or without chest pain, and syncope/presyncope. Recommendations by the ACC/AHA include obtaining a detailed family history through three generations,[1] though this may prove difficult in a busy ED. Physical exam may reveal a systolic murmur most prominent at the area of maximal impulse as well as an S4. Patients with systolic anterior motion of the mitral valve may have LVOTO that presents as a harsh crescendo-decrescendo murmur over the left sternal border. The effects of provocative maneuvers are shown below.

Figure 2: Provocative maneuvers for HCM murmur. (Source: https://www.osmosis.org/learn/Hypertrophic_cardiomyopathy)

ECG Findings

A normal ECG is found in only 4% to 25% of patients with HCM, making ECG interpretation a low-cost and widely available diagnostic modality to emergency physicians.[1,2,3] Though ECG abnormalities do not reliably correlate with the severity or pattern of HCM, they may demonstrate evidence of Left Ventricular Hypertrophy (LVH), arrhythmias, and repolarization abnormalities defined as ST-segment depression/elevation > 0.1 mV below or above the J-point in at least two leads (or >0.2 mV if V1, V2, or V3).

Figure 3: Table of ECG findings in HCM.[2,4,5]

Patients with a QRS > 120, a ‘pseudo-STEMI’ pattern, and low QRS voltage has an associated increased risk of sudden cardiac death (SCD).[2] Distinguishing the ECG patterns of HCM from those with a normal variant or those of athletes is a topic outside the scope of this talk, though there exist criteria that help differentiate these patient populations.[6] More discussion on common normal variants can be found here.

Figure 4: Prevalence of ECG findings in patients with HCM.[4] Figure 5: Examples of ECG findings of HCM.[2]

When we return to our patient’s ECG, we can see patterns consistent with HCM, including ‘pseudo-STEMI’ pattern, QRS fragmentation, LVH, and diffuse deep T wave inversions. However, we know that ECG findings are not diagnostic by themselves, so we move on to echocardiography.

Echocardiography

HCM is diagnosed in adults when either a 2D echo or Cardiac Magnetic Resonance (CMR) reveals a maximal end-diastolic wall thickness of ≥ 15 mm anywhere in the left ventricle in the absence of another cause of hypertrophy.[1] The cutoffs are different if there is a family history of HCM or if the patient is pediatric. When HCM is suspected, a comprehensive 2D echo should be performed to confirm the diagnosis. Of note, echo may miss certain HCM phenotypes, necessitating the use of CMR.[7] Given the complexity of these images and the resources required to obtain these images, this should be left to our cardiology colleagues and echocardiography technicians.

Acknowledging the concern for indication creep,[8] the measurement of LV wall thickness is performed and is most accurate in the parasternal short-axis at end-diastole,[9] a view that can easily be obtained at bedside with point-of-care ultrasound. Though LV wall thickness ≥ 15 mm is not 100% specific for the diagnosis of HCM,[10] it could raise your suspicion of the underlying pathology in your patient. Examples of more advanced echo techniques performed by emergency physicians are emerging, though emergency physicians should refrain from making definitive decisions regarding advanced echo findings unless adequately trained.

Figure 6: Parasternal long and short view of a patient with HCM.[11]

Treatment

Generally, treatments for patients with HCM target symptom management and prevention of sudden cardiac death, and advances in treatment modalities have reduced HCM mortality from 6% per year to as low as 0.5% per year.[12] Pharmacological options for symptomatic patients include beta-blockers as first-line therapy, calcium channel blockers as second-line, and disopyramide for those with refractory symptoms. All drug classes, through negative inotropy and chronotropy, decrease LVOTO, increase diastolic filling, and improve overall heart function. However, these medications do not prevent disease progression or reduce sudden death risk.[12,13] Providers should avoid medications that promote LVOTO, such as vasodilators and high-dose diuretics. Patients with severe LVOTO who fail pharmacologic treatments are candidates for invasive treatment, usually surgical myomectomy or alcohol septal reduction.

Emergent conditions

For patients presenting with acute hypotension, special attention needs to be paid to maximizing preload with IV fluids and afterload with vasopressors (preferably phenylephrine or vasopressin) and avoiding increases in heart rate and contractility, as this may worsen the LVOTO. For this reason, inotropes are not recommended. If there is suspicion of LVOTO as the primary cause of hemodynamic compromise, beta blockade with esmolol may be considered, as prior evidence has shown significant decreases in LVOT pressure gradients after administration, though notably this was in patients with Takotsubo cardiomyopathy.[14] Those patients with presentations suggesting volume overload may respond to low-dose diuresis, keeping in mind that high-dose diuresis may exacerbate the LVOTO.

Patients with HCM may have poor tolerance of atrial fibrillation, occasionally making electrocardioversion necessary. Though a rhythm-control strategy with cardioversion or antidysrhythmic drugs is advised, rate-control with intravenous beta-blockers or calcium channel blockers may be used.[1] These patients all require anticoagulation, with CHA2DS2-VASc score being unreliable in patients with HCM.[15]

For patients presenting with ventricular dysrhythmias, management per ACLS is advised to restore sinus rhythm. First-line treatment to prevent recurrence includes initiation of beta-blockers.[1] Amiodarone is recommended for recurrent ventricular dysrhythmias despite beta-blocker therapy, though this data is extrapolated from patients without HCM. Those who continue with ventricular dysrhythmias despite beta blocker and antidysrhythmic therapy may require ablation.[1]

Prevention of Sudden Cardiac Death

The use of implantable cardioverter defibrillators (ICD) in patients with HCM, which has been shown to reduce mortality,[16] takes into account risk stratification tools, clinical judgment, and shared decision-making with an informed patient. Patients with HCM who have had an episode of SCD in the past, ventricular fibrillation, or sustained ventricular tachycardia have a class 1 recommendation for ICD placement for secondary prevention.[1]

Risk factors for SCD include family history of SCD from HCM, massive LVH (for adults ≥ 30 mm of wall thickness), unexplained syncope, LV systolic dysfunction (EF < 50%), left ventricular apical aneurysm, extensive late gadolinium enhancement (≥15% of LV mass), and non-sustained ventricular tachycardia.[1] Though many of these risk factors are identified on more advanced imaging, those identified as having HCM with unexplained syncope, family history of SCD from HCM, or non-sustained ventricular tachycardia may be identified early by emergency physicians and referred to cardiology for possible ICD and primary prevention of SCD.

Disposition

Patients suspected of having HCM who are asymptomatic without signs of heart failure, new atrial fibrillation, or other arrhythmias can be discharged with outpatient cardiology follow-up for more advanced imaging (echo, cardiac MR) and possible ambulatory ECG, exercise echo, and genetic testing. Those with established HCM who are asymptomatic may be discharged and followed for disease progression and risk stratification assessment. Patients with suspected or established HCM who are symptomatic or hemodynamically unstable should be admitted with cardiology consultation. Patients with new atrial fibrillation or other dysrhythmias may warrant admission for cardiac monitoring and possible medication initiation.

Back to the Patient

After coronary angiography, the patient returned to CCU for cardiac monitoring. Although this patient had no episodes of syncope, he had runs of sustained ventricular tachycardia, an indication for ICD placement. Cardiology placed an ICD, and the patient was discharged on metoprolol and diltiazem.

Take Home Points:
- Classic ECG findings of HCM include LVH, pathologic ‘dagger’ Q waves, deep S waves in V1-V3, and high R wave in V4-V6 with abnormal T waves - these findings are not diagnostic
- A bedside parasternal short axis view at end-diastole may reveal wall thickness ≥ 15 mm and increase suspicion for HCM
- Emergent treatment involves use of beta-blocker or calcium channel blockers, avoiding vasodilators and high-dose diuretics, and prompt treatment of atrial fibrillation and ventricular dysrhythmias.