DISCUSSION

ApHCM is a mostly non-obstructive asymptomatic cardiomyopathy.Reference Sakamoto, Amano and Hada ^{4 -} Reference Eriksson, Sonnenberg and Woo ⁶ In rare situations in which patients are symptomatic, they may present with adverse sequelae including heart failure (related to LV diastolic dysfunction and elevated filling pressures),Reference Webb, Sasson, Rakowski, Liu and Wigle ¹² angina, syncope, arrhythmia including atrial fibrillation, stroke from apical thromboembolism, and sudden cardiac death.Reference Jan, Todaro, Oreto and Tajik ^{13 ,} Reference Moon, Shim and Ha ¹⁴ ApHCM was historically regarded as a phenotype largely unique to Japanese patients, in whom it was first described. It occurs more frequently in the Japanese population, with one comparative study revealing apical variants accounting for 15% and 3% of all hypertrophic cardiomyopathy within Japanese and Minnesotan cohorts, respectively.Reference Kitaoka, Doi and Casey ¹⁵ Smaller studies have suggested a prevalence between 3% and 11% in North American cohorts.Reference Chikamori, Doi and Akizawa ^{1 ,} Reference Eriksson, Sonnenberg and Woo ^{6 ,} Reference Wigle, Sasson and Henderson ^{16 ,} Reference Cannan, Reeder, Bailey, Melton and Gersh ¹⁷ The etiology of ApHCM is multifactorial, with studies suggesting variants with a genetic predispositionReference Towe, Bos, Ommen, Gersh and Ackerman ¹⁸ and also demonstrating exclusive development during adulthood.Reference Sakamoto, Amano and Hada ⁴ A family history is uncommon,Reference Sakamoto, Amano and Hada ^{4 ,} Reference Klarich, Attenhofer Jost and Binder ¹⁹ and genomic data regarding inheritance patterns, penetrance, and expressivity of known genetic mutations are presently unknown.Reference Towe, Bos, Ommen, Gersh and Ackerman ¹⁸

Classically described ECG findings comprise “giant negative T waves (greater than 10 mm) associated with high QRS voltage (R wave greater than 26 mm in lead V5 or the sum of the S wave in lead V1 and the R wave in lead V5 35 mm or more).”Reference Yamaguchi, Ishimura and Nishiyama ³ These voltage criteria may be related to both LV hypertrophy or to differences in localized wall thickness leading to disparities in the duration of repolarization.Reference Sakamoto, Tei and Murayama ² Later studies emphasized any precordial giant negative T waves as the hallmark of ApHCM, although giant negative T waves may be present in as little as 11% of American Caucasian patients with ApHCM.Reference Klarich, Attenhofer Jost and Binder ¹⁹ Giant negative T waves diminish with ageReference Eriksson, Sonnenberg and Woo ⁶ and are significantly more common in Japanese patients.Reference Kitaoka, Doi and Casey ¹⁵ Notably, giant negative T waves may be seen in myocardial ischemia, right ventricular hypertrophy, electrolyte abnormalities, hypertensive heart disease, and cerebrovascular disease.Reference Sakamoto, Tei and Murayama ^{2 ,} Reference Yamanari, Saito and Mikio ^{20 ,} Reference Jacobson and Schrire ²¹

Echocardiographic criteria described in research protocols include two-dimensional echocardiography showing asymmetric LV hypertrophy with apical predominance, an apical wall thickness of >15 mm, and a ratio of maximal apical to LV posterior wall thickness of >1.5 at end-diastole.Reference Eriksson, Sonnenberg and Woo ⁶ An end-diastolic “ace-of-spades” configuration on left ventriculography is considered pathognomonic for ApHCM. Moreover, this may reveal a midventricular obstruction and an apical aneurysm, two potentially overlapping morphologies with significant clinical implications.Reference Minami, Haruki and Hagiwara ⁵ Cardiac MRI may facilitate diagnosis even if echocardiography or ventriculography fail to help in the diagnosis of ApHCM initiallyReference Eriksson, Sonnenberg and Woo ⁶ and may allow for early detection in the absence of the “ace-of-spades” configuration.Reference Suzuki, Shimamoto and Nishikawa ²²

Chest pain mimicking ACS in the setting of ApHCM has been previously reported,Reference Cubukçu, Scott and Williams ^{8 ,} Reference Olearczyk, Gollol-Raju and Menzies ^{10 ,} Reference Diaconu, Dumitru, Fruntelata, Lacau and Bartos ¹¹ including ST-segment elevation in contiguous leads resulting in the administration of thrombolytics,Reference Lin, Chen and Ding ^{7 ,} Reference Sayin, Koçum and Kervancioglu ⁹ as in this case. If patients with ApHCM develop angina, several mechanisms have been proposed. Apical infarction may occur because of systolic midventricular obstruction from cavitary obliteration, with subsequent diminished coronary perfusion or high wall tension from an apical aneurysm.Reference Lin, Chen and Ding ⁷ Impaired diastolic relaxation or systolic compression of vessels by a hypertrophied myocardial mass may result in inadequate coronary flow.Reference Cubukçu, Scott and Williams ^{8 ,} Reference Jan, Todaro, Oreto and Tajik ¹³ Lastly, there may be a component of a supply-demand mismatch with an increased apical myocardial mass without sufficient coronary perfusion.

There is no specific treatment for ApHCM.Reference Olearczyk, Gollol-Raju and Menzies ¹⁰ Patients should be referred to a cardiologist for risk stratification, monitoring, and management. Given the heterogenous clinical spectrum, medical therapy is directed toward specific symptoms, including the judicious use of beta-blockers and diuretics for angina, arrhythmia, and heart failure. Patients with a concomitant apical aneurysm have a particularly poor prognosis.Reference Chen, Lei, Hsu, Chung and Sung ²³ Overall survival has ranged greatly from 47% at 20 yearsReference Klarich, Attenhofer Jost and Binder ¹⁹ to 95% at 15 years,Reference Eriksson, Sonnenberg and Woo ⁶ with heterogeneity in age at the first presentation playing a role in the discrepancies.

The diagnosis of ApHCM can prove challenging if patients present with acute chest discomfort and an abnormal ECG. Integral components of the initial diagnostic process in this instance include a careful evaluation of coronary risk factors, quality of chest discomfort, ECG pattern and progression, and cardiac biomarker evolution. Despite these factors, if patients present without a known history of apical hypertrophy, activation of ACS protocols with reperfusion may be warranted based on the best evidence available to clinicians at the time. While ApHCM may interfere with the clinical diagnosis because of ECG findings indicating infarction, it is equally as important to consider alternative explanations for chest pain in this setting.

In a retrospective evaluation of this case, given the equivocal ECG and lack of cardiac biomarker elevation, point-of-care echocardiography (POCE) may have been useful in distinguishing ApHCM from ACS, leading one to consider causes of pain such as a supply-demand mismatch as opposed to plaque rupture resulting in STEMI. The use of POCE in the setting of suspected ACS to recognize regional wall-motion abnormalities has been studied,Reference Kontos, Arrowood, Paulsen and Nixon ²⁴ including by emergency physicians using a standardized protocol.Reference Frenkel, Riguzzi and Nagdev ²⁵ Kerwin and others have demonstrated that with brief standardized training, emergency physicians can improve their ability to recognize regional wall-motion abnormalities.Reference Kerwin, Tommaso and Kulstad ²⁶ In the ED, the absence of regional wall-motion abnormalities on POCE has been used to rule out ACS in the setting of ST-segment elevation resulting from pulmonary embolismReference Shy, Gutierrez and Strayer ²⁷ and hypercalcemia.Reference Strand, Aung and Agarwal ²⁸ Herein, we suggest that POCE performed in the ED with the support of a cardiologist may have allowed for recognition of the apical hypertrophy as the cause of the patient’s ECG findings.

Our case illustrates the complex manner in which ApHCM may present in the era of rapid early reperfusion therapy. It should reinforce the idea that not all chest pain with simultaneous ST-segment elevation is a result of myocardial infarction. For patients with ECG findings suggestive of alternate diagnoses, POCE may be useful in guiding further management.