Utility of Cardiac Computed Tomography in the Diagnosis of Apical Hypertrophic Cardiomyopathy: A Case Series

Abstract

Hypertrophic cardiomyopathy (HCM) is characterized by abnormal thickening of the left ventricular myocardium. Apical HCM is a less common variant of HCM where the hypertrophy is limited to the apical segments and can be challenging to diagnose based on traditional echocardiography alone. Patients with HCM can present with exertional angina. We present a series of four different cases, where patients were advised computed tomography (CT) coronary angiography for the evaluation of coronary artery disease. While CT coronary angiography excluded obstructive coronary artery disease, a detailed evaluation of the retrospective electrocardiogram-gated CT coronary angiography data helped in establishing the diagnosis of apical HCM in these patients. We discuss the importance of a systematic analysis of cardiac CT for diagnosing HCM variants and highlight the utility of reconstructed static and cine CT images which are readily available from the data obtained during retrospective gated CT coronary angiography for diagnosing HCM.

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is characterized by abnormal thickening of the left ventricular myocardium. The most common form of HCM is associated with asymmetric septal hypertrophy and left ventricular outflow tract obstruction. The diagnosis is easily established based on clinical examination and echocardiographic features. Less common forms of HCM include midcavitary HCM and apical HCM. These variants may be difficult to diagnose using echocardiography alone. The left ventricular apex is poorly visualized on standard transthoracic echocardiography (TTE) and apical HCM can be missed.[1] Patients often present with exertional angina and are advised for further imaging to evaluate for coronary artery disease (CAD) which yields normal coronaries or nonobstructive CAD.[2] We present four cases where patients were advised computed tomography coronary angiography (CTCA) to evaluate for CAD. While CTCA excluded obstructive CAD, a detailed evaluation of the retrospective electrocardiogram (ECG)-gated CTCA data helped in establishing the diagnosis of apical HCM. We discuss the importance of a systematic analysis of cardiac CT for diagnosing HCM variants and highlight the utility of reconstructed CT images and cine CT which are readily available from the data obtained during CTCA for diagnosing HCM.

CASE PRESENTATION

Case 1

The patient was a 30-year-old obese man with history of hypertension for six years. His blood pressure was well controlled with a single antihypertensive agent. The patient also complained of exertional dyspnea for the past 6 years and exertional angina for the past 4 years. His functional status was New York Heart Association (NYHA) Class II. The examination revealed a left ventricular S4. No murmurs were present. The ECG showed evidence of left ventricular hypertrophy (LVH) and inverted T waves in the precordial leads. The initial echocardiogram was reported as showing severe concentric LVH. Workup for secondary causes of hypertension was negative. The patient was advised a CTCA to evaluate for CAD. It showed normal coronaries, with the presence of profound LVH, disproportionately higher in the apical regions [Figures 1 and 2]. In addition, superficial myocardial bridging of the mid-early distal left anterior descending (LAD) artery was seen. The maximal diastolic phase thickness obtained on CT was 25 mm. Long-axis cine CT images showed systolic obliteration of the apex similar to invasive left ventriculography [Supplementary Video 1]. The patient had a metallic bone implant which precluded cardiac magnetic resonance imaging (MRI). The patient was advised beta-blockers, ambulatory ECG monitoring, and family screening.

Figure 1.

Computed tomography images in diastolic (a) and systolic (b) phases showing systolic obliteration of left ventricle apex with myocardial hypertrophy, maximum measuring 25 mm in the apical region in end diastole (c). LA: Left atrium, LV: Left ventricle

Figure 2.

Curved multiplanar (a-c), volume rendered (d), and axial (e) computed tomography coronary angiography images showing normal coronaries with superficial myocardial bridging of mid-early distal left anterior descending coronary artery (region within dots in c and e). LAD: Left anterior descending, RCA: Right coronary artery, LCX: Left circumflex coronary artery

Case 2

The patient was a 50-year-old lady with history of diabetes mellitus and hypertension. She presented with exertional angina for the past 3 years. Her blood pressure was well controlled with a single antihypertensive agent. The cardiovascular examination was unremarkable. The ECG showed LVH and inverted T waves in the precordial leads. An initial echocardiogram was reported to have concentric LVH. In view of risk factors and exertional angina, the patient was advised of CTCA. It showed normal coronaries with superficial myocardial bridging of the early distal LAD artery [Figure 3]. Detailed evaluation of the CTCA data showed apical hypertrophy of the myocardium with a maximum diastolic phase thickness of 17.6 mm [Figure 4]. Cine CT images confirmed systolic obliteration of the apex [Supplementary Video 2]. A cardiac MRI was performed, which also showed apical myocardial hypertrophy with no evidence of myocardial fibrosis. The patient was advised beta-blockers, ambulatory ECG monitoring, and family screening.

Figure 3.

Curved multiplanar (a-c), volume rendered (d), and axial (e) computed tomography coronary angiography images showing normal coronaries with superficial myocardial bridging of early distal left anterior descending coronary artery (region within dots in b and e). LAD: Left anterior descending, RCA: Right coronary artery, LCX: Left circumflex coronary artery

Figure 4.

Computed tomography images in diastolic (a) and systolic (b) phases showing systolic obliteration of left ventricle apex with myocardial hypertrophy, maximum measuring 17.6 mm in the apical region end diastole (c). LA: Left atrium, LV: Left ventricle

Case 3

The patient was a 70-year-old man with a history of hypertension for the past 20 years that was well controlled on a single antihypertensive agent. The patient had Class II exertional dyspnea. The examination was unremarkable. The ECG showed LVH and inverted T waves in the precordial leads. The echocardiogram was reported as having concentric LVH. CTCA showed no significant obstructive CAD. Detailed evaluation of the CTCA data and the cine CT images showed LVH in the apical segments (maximum diastolic phase thickness of 16.5 mm) with systolic obliteration and a small apical aneurysm [Figure 5 and Supplementary Video 3]. A review of the echocardiogram confirmed apical thickening and flow acceleration in the left ventricle with a peak gradient of 30 mmHg. The echocardiogram could not identify the apical aneurysm. The cardiac MRI confirmed apical hypertrophy and an apical aneurysm with no evidence of myocardial fibrosis. The morphological features were consistent with mixed apical HCM. The patient was advised beta-blockers, ambulatory ECG monitoring, and family screening.

Figure 5.

Computed tomography images in diastolic (a) and systolic (b) phases showing systolic obliteration of left ventricle apical region with apical aneurysm (*) and myocardial hypertrophy, maximum measuring 16.5 mm in the apical region in end diastole (c). LA: Left atrium, LV: Left ventricle

Case 4

A 40-year-old man presented with complains of exertional angina and dyspnea for five years. His functional status was NYHA Class II. The patient had presented with chest pain five years back in another hospital where he was diagnosed with hypertension and suspected to have acute coronary syndrome based on ST-T changes in the ECG. He was on a single antihypertensive agent. The ECG showed LVH with fixed T wave inversion in the precordial leads. The echocardiogram was reported to have concentric hypertrophy. A CTCA was advised to rule out CAD. It showed normal coronaries with intramural course of the distal right coronary artery, along the wall of the right atrium [Figure 6]. Evaluation of the CTCA data for cardiac function showed apical hypertrophy with a small apical aneurysm confirming the diagnosis as mixed apical HCM [Figure 7 and Supplementary Video 4]. No thrombus was seen within the aneurysmal sac. A review of the echocardiogram confirmed flow acceleration in the apical segment, but an aneurysm could not be visualized. A cardiac MRI subsequently showed similar findings confirming the diagnosis of mixed apical HCM with an apical aneurysm. The patient was advised beta-blockers, ambulatory ECG monitoring, and family screening.

Figure 6.

Curved multiplanar (a-c), volume rendered (d), and axial (e) computed tomography coronary angiography images showing normal coronaries with intramural course of distal right coronary artery (region within dots in b and e). RCA: Right coronary artery, LCX: Left circumflex coronary artery, LAD: Left anterior descending

Figure 7.

Computed tomography images in diastolic (a) and systolic (b) phases showing systolic obliteration of left ventricle apical region with apical aneurysm (*) and myocardial hypertrophy measuring 17.5 mm in the apical region in end diastole (c). LA: Left atrium, LV: Left ventricle

DISCUSSION

Apical HCM is a variant of HCM, in which the myocardial hypertrophy is predominantly in the apical segments below the papillary muscles. It was first described in Japan; however, it is now recognized to be prevalent in other regions of the world as well. Initially thought of as a benign form of HCM, recent studies have shown that the prognosis is similar to classical HCM.[3,4] The diagnostic criteria used in the initial studies required ECG changes of LVH with deep inverted T waves and left ventriculography showing the spade-like appearance of the LV cavity in diastole with systolic obliteration.[5,6] Currently, the diagnostic criteria are based on echocardiography or cardiac MRI showing absolute LV wall thickness ≥15 mm with apical-to-posterior wall ratio ≥1.5.[7] Apical HCM can have two types: pure apical HCM or mixed apical.[8,9] In pure apical HCM, the hypertrophy is restricted to the apical segments distal to the papillary muscle, while in mixed form, hypertrophy is present in other segments also but maximum in apical segments.[9] Apical aneurysms can be associated with apical HCM and are more common in the mixed form.

In the present study, all four patients were initially diagnosed to have concentric LVH. The CT allowed diagnosis of HCM and helped categorize them into pure and mixed forms. The findings were confirmed by cardiac MRI in 3 of the 4 patients. Further, CT was able to correctly identify apical aneurysms in two patients which were missed on the TTE. An apical aneurysm is an important modifier for assessing the risk of sudden cardiac death. In one patient, CMR was precluded because of an orthopedic implant, but the entire clinical picture was consistent with HCM. This demonstrates the utility of CT in diagnosing HCM and its variants in patients where MRI may not be feasible.

Standard TTE can miss apical HCM. In one study, TTE could not diagnose nearly one-third of the patients with apical HCM.[9] This is because the apex is not well visualized in standard views.[1,10] The diagnostic yield of TTE can be increased using echocardiographic contrast agents, which improves the delineation of the endocardial border.[11] TTE may also miss apical aneurysms in patients with HCM.[8]

All patients in the present series had a history of hypertension and were well controlled on a single antihypertensive when referred for evaluation. Hypertension was likely coincidental or misdiagnosed previously based on ECG features of LVH. ECG and echocardiographic features of LVH which are disproportionate to the clinical presentation should raise suspicion for HCM and prompt evaluation.

Patients with HCM may present with angina and are often misdiagnosed to have CAD.[2] This is because of microvascular dysfunction and demand-supply mismatch due to hypertrophy.[12] Such patients may be referred for CTCA for the evaluation of chest pain. Besides coronary anatomy, CT also provides valuable data related to the left ventricular structure and function, which can help in the diagnosis of HCM and its variants.[13] CT permits morphologic assessment of all left ventricular wall segments. CT also facilitates the identification of other structural anomalies such as myocardial bridging which may contribute to the anginal symptoms in these patients.

Cine CT imaging is a useful but underutilized tool that allows the assessment of the dynamic function of the left ventricle and understanding of the contraction in various phases similar to the catheter left ventricular angiography. Cine loops are obtained by reconstruction of images acquired during a CT coronary angiogram. Further, using the maximum intensity projection tool and adjusting slice thickness to 2–3 mm, cine loops similar to catheter ventriculography can be obtained [Supplementary Videos 1-4]. In patients with apical HCM, cine imaging in vertical long-axis view shows a characteristic “spade-like” configuration of the left ventricular cavity in diastole with obliteration of the apex in systole.[14] However, unlike traditional catheter angiograms which is obtained in a single view, the CT cine angiogram can be reconstructed in multiple views using full datasets generated from retrospective ECG-gated cardiac CT for a better understanding of morphology and function. CT also correctly identifies segments of the intramural course of coronary arteries, which has been reported more commonly in patients with HCM.[15] The intramural course of coronary arteries was seen in three out of four patients in the present study.

CONCLUSION

This case series highlights the utility of cardiac CT in diagnosing apical HCM and related morphological features such as apical aneurysm and myocardial bridging. Apical HCM is easily missed on echocardiography and patients often undergo cardiac CT for ruling out coronary artery disease due to similar presenting symptoms. A detailed analysis of LV structure and function using CT data obtained for coronary evaluation can help in diagnosing apical HCM which can be confirmed with gold standard MRI evaluation.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.