Case Presentation: A 29-year-old man with a history of exercise-induced asthma presented with left-sided chest pain and exertional dyspnea. Two weeks ago, he started experiencing chest pain when playing basketball. The pain was relieved with rest. Prior to current admission, he was treated for asthma exacerbation for similar symptoms at a community hospital. He continued to experience chest pain despite treatment. On exam, he described his pain as chest tightness that was dull in nature, non-radiating, non-positional. Vital signs were within normal range; lab work was unremarkable with negative serial troponins. EKG showed a previously known asymptomatic 1st degree AV block but no STEMI or NSTEMI. Patient did not report any family history of sudden death or cardiac arrhythmias. He denied smoking or use of recreational drugs. He coaches and frequently plays basketball. Our initial differential diagnostic included respiratory condition (exercise-induced asthma) versus cardiac condition (hypertrophic cardiomyopathy, cardiac arrhythmias). To elucidate the etiology of the patient’s chest pain, we performed a battery of imaging tests. Transthoracic echocardiography (TTE) revealed a normal ejection fraction (EF 65%) with hypermobility of papillary muscles. At this moment, hypertrophic cardiomyopathy (HCM) was our leading diagnosis. On exercise stress echocardiography, he had normal left ventricular obstruction tract (LVOT) gradient at rest; the gradient dramatically increased with exercise (122 mmHg). After the patient was adequately dehydrated, we performed a transesophageal echocardiography with amyl nitrite to determine the cause of LVOT obstruction (dehydration vs hypertrophied papillary muscles). Of note, amyl nitrite is used diagnostically to provoke obstructive physiology across LVOT (2). There was prominent posterolateral papillary muscle; no LVOT gradient change with administration of amyl nitrite was noted. This result suggests that dehydration, not hypertrophy of papillary muscles, was the cause for the high LVOT gradient seen on stress echocardiography.
Discussion: Hypertrophic cardiomyopathy is characterized by ventricular hypertrophy that can present with or without obstruction of LVOT. Approximately 75% of HCM patients have LVOT obstruction which increases their risk of a cardiac event (1). Most symptomatic patients experience sudden cardiac death as the first manifestation of HCM; this is a common occurrence in young active athletes (3). Thus, it is important to make a proper HCM diagnosis and initiate life-saving treatment. Here we highlight a diagnostic approach for suspected HCM. Stress echocardiography and TEE with amyl nitrite can help reveal anatomical anomalies potentially responsible for HCM and define the presence and nature of obstructive physiology across LVOT. This case also illustrates how the cognitive bias can lead to diagnosis error. On first hospital presentation, it was reasonable to consider asthma exacerbation as a potential cause of the patient’s chest pain. However, the nature of his chest pain should have prompted a more thorough investigation or referral for diagnosis of critical conditions such as cardiac hypertrophy. In such cases, it is essential to explore other diagnoses that can have significant consequences if missed.
Conclusions: In suspected HOCM, clinicians should consider using TEE with amyl nitrite as a diagnostic tool for differentiation of dehydration versus hypertrophy of papillary muscles as cause of obstructive physiology.