Hypertrophic Cardiomyopathy Part 1: Chest Pain

Co-authors: Taylor Murtaugh MD, Esteban Davila MD

The Case

A 59-year-old male with a past medical history of hypertension, hyperlipidemia, and gastroesophageal reflux disease was brought in by EMS to the ED with severe chest pain. EMS administered 324 mg of aspirin. The patient endorsed left-sided chest pain while ambulating with associated lightheadedness and diaphoresis. He denied shortness of breath, syncope, nausea, vomiting, fevers, or chills. He endorsed a similar episode of less severe chest pain in the past, where cardiac magnetic resonance imaging was performed. He did not know the results and was not taking any medications. The patient also had a coronary angiogram 15 years ago that did not reveal atherosclerosis. The patient was afebrile with heart rate 105/min, respiratory rate 20/min, blood pressure 210/100 mm Hg, and SpO2 100% on room air. Exam revealed an uncomfortable-appearing male with diaphoresis, clear lungs, s1 and s2 with no murmur, non-tender abdomen, no jugular venous distention, and no lower extremity edema.

The initial ECG is below:

Figure 1: Initial ECG

ECG Interpretation: Sinus tachycardia at ~100/min, normal axis, and slightly prolonged QTc. There is evidence of ST-elevation in aVR and V1 with diffuse ST-depression in all other leads. There is bizarre QRS fragmentation in lead V2 and V3 as well as large QRS amplitudes in the lateral leads fulfilling seaman’s sign (touching or crossing QRS complexes in the precordial leads; 92% specificity for predicting LVH) suggesting left ventricular hypertrophy (LVH);[1] LVH “strain” pattern is demonstrated in the lateral leads.

Given the chest pain and diaphoresis, the ED physicians were concerned about aortic dissection and abdominal aortic aneurysm. The ED physicians administered morphine, and CTA aorta was negative for these pathologies. The initial troponin I returned elevated at 0.14 ng/mL, and the patient was admitted to medicine for management of suspected "non-ST elevation myocardial infarction". A repeat troponin I 5 hours later was 24 ng/mL, at which point the primary team ordered a repeat ECG shown below.

Figure 2: Repeat ECG

ECG interpretation: Normal sinus rhythm. The axis is normal. The ST-elevation in aVR and V1 remains, though now has a more concave pattern; the diffuse ST-depression is resolved. The QRS fragmentation in V3 remains, and there is now diffuse, deep T wave inversion in V2-V6, I, aVL, and II. There remains evidence of LVH.

Given the symptoms of acute myocardial ischemia and a rising troponin (meeting the 4th universal definition of myocardial infarction), Cardiology was consulted with concern for acute myocardial infarction.[2] Emergent left heart catheterization revealed a right dominant coronary system and angiographically normal coronary arteries. An echocardiography during the cardiac catheterization revealed severe LVH predominantly in the apex, suggestive of possible apical hypertrophic cardiomyopathy (HCM). Records obtained from the patient’s outside cardiologist confirmed apical HCM on prior echo and cardiac magnetic resonance imaging. So what caused this troponin elevation, and could we have identified the HCM earlier?

Hypertrophic Cardiomyopathy

HCM, previously known as hypertrophic obstructive cardiomyopathy, is one of the most commonly inherited cardiac disorders with a prevalence in the general population of 1:200-1:500. It is one of the leading causes of sudden cardiac death in young people.[3,4] Because one-third of patients with HCM remain nonobstructive, the name has been changed from hypertrophic obstructive cardiomyopathy to HCM.[5] The AHA/ACC defines HCM as “LVH in the absence of another cardiac, systemic, or metabolic disease capable of producing the magnitude of hypertrophy evident in a given patient and for which a disease-causing sarcomere (or sarcomere-related variant) is identified, or genetic etiology remains unresolved.”[5] Essentially, HCM is a diagnosis of exclusion. Because of this, HCM will rarely be definitively diagnosed in the ED, but a high level of suspicion can trigger the workup for this condition.

The pathophysiology of HCM includes a complex interplay of left ventricular outflow tract obstruction (LVOTO), mitral regurgitation, diastolic dysfunction, myocardial ischemia, arrhythmias, and autonomic dysfunction.[5] Although classically thought of as septal hypertrophy leading to LVOTO, multiple variants have been identified. Variants including concentric, reverse septal, neutral, and apical HCM have been identified, and nearly any pattern of LV wall thickening can occur with HCM. Although commonly linked together, neither systolic anterior motion nor hyperdynamic LV function is required for diagnosis.

Most patients with HCM do not have limiting symptoms or need for advanced treatments, and many are diagnosed with HCM after age 60.[5] However, those who have known pathogenic sarcomeric gene variants or those diagnosed earlier in life have a higher lifetime risk of adverse events.[6] Common adverse events include sudden cardiac death, symptoms secondary to left ventricular outflow tract obstruction or diastolic dysfunction, heart failure symptoms, and arrhythmias, notably atrial fibrillation with risk of thromboembolic stroke. Knowledge of these adverse events is important for emergency physicians, as a prior population-based study on ED utilization by patients with HCM demonstrated that these patients often present for the cardiovascular complications listed above.[7]

Figure 1: Primary diagnosis from ED assigned by discharge to patients with HCM.[7]

Chest Pain

Anginal chest pain is common in patients with HCM with reports as high as 70% in a conceptual model based on patient interviews and web surveys.[8] Patients with HCM may develop obstructive coronary artery disease with a prevalence of 11% to 26%, and those with severe CAD have associated increases in mortality and sudden cardiac death.[9,10] However, myocardial ischemia can occur in patients without CAD. The pathophysiology of anginal chest pain in HCM is related to increased oxygen demand secondary to hypertrophy, microvascular dysfunction, and small coronary vessel medial hypertrophy, which causes decreased coronary flow reserve and regional myocardial ischemia. One study in patients with HCM demonstrated scintigraphic evidence of myocardial ischemia in patients with normal coronary arteries on cardiac catheterization, further demonstrating the risk of myocardial ischemia and infarction in patients with HCM.[11]

Now that we know general information about HCM, how can we remember to consider this diagnosis in the ED? The initial clues for HCM in the ED can be obtained through a thorough history of present illness, identification of a family history of HCM, a good physical exam including auscultation for a heart murmur, an abnormal ECG, and an echo with abnormalities that we will discuss later. In Part 2 of this discussion, we will discuss each of these components with particular emphasis on ECG, echo, treatment, and disposition.

Take Home Points:

• HCM includes a complex interplay of left ventricular outflow tract obstruction, mitral regurgitation, diastolic dysfunction, myocardial ischemia, arrhythmias, and autonomic dysfunction
• Common adverse events include sudden cardiac death, symptoms of left ventricular outflow tract obstruction, heart failure, and arrhythmias 
• Patients with HCM are at higher risk for myocardial ischemia even in the absence of CAD