Mid‐ventricular Hypertrophic Obstructive Cardiomyopathy with Apical Aneurysm Complicated with Syncope by Sustained Monomorphic Ventricular Tachycardia

Abstract

Mid‐ventricular hypertrophic obstructive cardiomyopathy with secondary formation of apical aneurysm is a rare variant of hypertrophic cardiomyopathy. They have a unique behavior because unlike other variants it causes sustained monomorphic ventricular tachycardia, which makes it particularly severe.

ID: ILP, Caucasian, male, 53 years old. Main complaint: sudden discomfort and syncope. History of current disease: Approximately 1 hour before, he started with profuse diaphoresis, dyspnea at rest, followed by syncope. Following electrical cardioversion, the patient himself reported being followed by a cardiologist and knowing to be a carrier of familial hypertrophic cardiomyopathy (HCM). He also recounted a son dying suddenly at age 18, during cycling. He is using β‐blockers. Physical: cold sweating, unconscious, and dyspnea. Tachycardic regular cardiac rhythm (heart rate: 185 bpm), without cannon “a” waves, changes in beat‐to‐beat systolic blood pressure or variations in the first heart sound intensity. Blood pressure: 80 × 60 mmHg. Peripheral pulses present without edema. Bilateral crackles in both lungs.

Figure 1 shows the admission tracing. After reversion, it was decided for an implantable cardioverter defibrillator (ICD). The ECG in Figure 2 was performed after the electrical cardioversion. Figure 3 shows the echocardiographic image.

Figure 1.

ECG diagnosis: Wide sustained QRS complex tachycardia, heart rate = 187 bpm, QRS axis in the right superior quadrant “no man's land or Northwest axis” (≈−175°), absence of fusion and/or capture beats, R wave in V₁, and QS pattern from V₂ to V₆. Conclusion: VT originated from apical focus.

Figure 2.

ECG diagnosis: Sinus rhythm, HR: 61 bpm, P wave duration (P = 145 ms), P axis (+60°), augmented P‐terminal forces (PTF‐V₁): left atrial enlargement, PR interval (260 ms): first degree AV block. QRS axis +5°, QRS duration 115 ms, and fQRS. The ST segment and T wave are in an opposite direction to the preceding QRS complexes in left leads: strain pattern.

Figure 3.

Echocardiographic image in apical two‐chamber view. Mid‐left ventricular narrowing in the mid‐septum. Turbulent flow high velocity within the middle section of the LV chamber. Mid‐LV gradient = 91 mmHg at rest. Diastolic thickness of intraventricular septum with 24 mm and diastolic posterior wall thickness with 31 mm. Apical aneurysm observed only with contrast (4.4 cm). Conclusion: MVHOCM complicated with apical aneurysm. LV: left ventricle.

Figure 4 shows the ventriculography.

Figure 4.

Left ventriculogram with hourglass aspect of the LV and large aneurysmal dyskinetic sac with stasis of contrast at the LV apex. Mid‐ventricular obstruction (arrow) with 91 mmHg of gradient.

Discussion

Mid‐ventricular hypertrophic obstructive cardiomyopathy (MVHOCM) is a rare variant of HCM that occurs in 1% of patient's carriers of this entity.1 It could be complicated by apical aneurysm, as in this case.2 It is characterized by asymmetrical hypertrophy in the middle part of the septum (mid‐cavity obstruction), causing high intraventricular pressure gradients between the middle and low part of the left ventricle (LV) cavity. The patients complicated with apical aneurysm by LV necrosis are a significant clinical subset that is under identified and potentially fatal because it causes a tendency to sustained monomorphic ventricular tachycardia (SMVT). In the pathogenesis of the apical myocardial necrosis has been suggested to be secondary to increase in postload and to apical pressure augmentation, microcirculation disease associated with a decrease in coronary flow reserve, decrease in coronary perfusion pressure, spasm, and coronary lumen narrowing.3 The mechanical compression of the coronary arteries may lead to acute infarction by spasm and microcirculation disease as a consequence of myocardial wall stress during systole in an acute fashion,4 causing a tendency to microthrombi and plaque rupture that may lead to apical aneurysm formation. The β‐blockers are the drugs of choice. Because of the hemodynamic instability, we opted for secondary prevention implanting an ICD.

The SMVT has reentry mechanism, within the aneurysm or micro‐reentry at the neck of it. Radiofrequency catheter ablation (RFCA) looking for the entrainment may remove the ventricular tachycardia (VT) reentry circuit. The ICD implant should be followed by the addition of pharmacological treatment or RFCA. This procedure is capable of abolishing the SMVT.5 Kono et al.6 presented a patient with MVHOCM associated to apical aneurysm and drug‐refractary SMVT. In the electrophysiology study, polymorphic VT/ventricular fibrillation was induced. The patient underwent ICD implant associated with RFCA.

Minami et al.7 investigated the prevalence, clinical features, and prognosis of MVHOCM. The population of the study included 490 patients with HCM. The diagnosis of MVHOCM (mid‐cavitary gradient ≥30 mmHg) was observed in 46 patients. This group was more symptomatic and with a greater tendency to sudden cardiac death (SCD). The formation of apical aneurysm was a marker of fatal arrhythmias. The following risk markers for SCD are present in our case: wall thickness >30 mm; resting mid‐ventricular gradient >30 mmHg8; positive family history of SCD in young first‐degree relatives; recording of syncope related to the events; and ECG with QRS fragmentation (fQRS).8 It is defined as narrow QRS complexes (<120 ms) with multiple notches in R and/or S waves: ≥4 spikes in a single lead or ≥8 spikes in right precordial leads (V₁–V₃).9, 10, 11 Also, fQRS is defined as the presence of one or more additional R′ wave in two contiguous leads, corresponding to a major coronary artery territory of ECG.12 The presence of fQRS points out scarred myocardium and it constitutes a noninvasive marker of fatal events.13 It has been described in coronary artery disease,14 dilated cardiomyopathy,15 HCM,16 arrhythmogenic right ventricular dysplasia/cardiomyopathy,17 cardiac sarcoidosis,18 Brugada syndrome,19 and acquired long QT syndrome.20 In this last case, it is a marker of the appearance of Torsade de Pointes.21

Conclusion

MVHOCM, when in association with apical aneurysm, frequently complicates with the SMVT, unlike other forms of HCM, the VTs of which are usually not sustained. This difference makes the mid‐ventricular obstructive form more severe, which indicates the need of implanting automatic ICD as a secondary prevention for SCD, in association to β‐blockers. The latter are aimed at decreasing the number of shocks by the device.

Ann Noninvasive Electrocardiol 2016;21(6):618–621