Background
Apical outpouching, including wall motion abnormalities and aneurysms, has been described in apical hypertrophic cardiomyopathy (ApHCM).
Methods
Between 1976 and 2006, 193 patients with ApHCM (120 men; overall mean age, 61 ± 17 years) were evaluated.
Results
Apical outpouching was found in 29 patients (15%) and in 22 of the 78 patients (28%) imaged with contrast echocardiography. Six patients had apical aneurysms, and 23 patients had hypokinesis with apical dilatation but no wall thinning. Apical outpouching was more common in patients with diastolic gradients out of the apex ( P < .001), corrected QT interval prolongation ( P < .001), increased apical wall thickness ( P = .01), and family histories of sudden cardiac death ( P = .03). Sudden cardiac death, resuscitated cardiac arrest, or discharge of an automated internal cardiac defibrillator, or a combination, was observed in 11 patients (6%) during follow-up. Atrial fibrillation (28%), ventricular tachycardia (20%), and stroke (11%) were also relatively common in this study. No difference was observed in overall mortality rate comparing patients with ApHCM with and without apical outpouching. Similarly, no differences were found in the rates of sudden cardiac death, resuscitated cardiac arrest, and discharge of an automated internal cardiac defibrillator. The impact of true aneurysms was not assessed in this study.
Conclusions
Cardiac complications appear commonly in patients with ApHCM, but they did not seem to be related to apical outpouching in the present analysis.
The morphologic variability of ventricular wall thickening in hypertrophic cardiomyopathy (HCM) has been recognized since the introduction of two-dimensional echocardiography. Ventricular hypertrophy may be asymmetrical or diffuse and may be obstructive or nonobstructive. Asymmetrical septal hypertrophy is the most common HCM variant, accounting for approximately 80% of cases. Apical HCM (ApHCM) is a less common pattern of HCM and may represent a genetically unique population. In Japan, ApHCM affects 13% to 25% of the total HCM patient group; in North America, it affects 3% to 11%. ApHCM presents with several distinct features; it has been reported that about 10% of patients with ApHCM have apical regional dysfunction or the formation of an apical outpouching or aneurysm in the presence of normal coronary arteries.
Previous reports described sustained ventricular tachycardia or sudden cardiac death in patients with ApHCM and left ventricular (LV) apical aneurysms, respectively. More recently, Maron et al. described a 2% incidence of apical aneurysms among 1,299 patients with HCM with any pattern of hypertrophy (i.e., including ApHCM and other patterns of HCM). That report showed that patients with apical aneurysms had a combined adverse event rate of 10.5% per year, including sudden death, appropriate implantable cardioverter-defibrillator discharges, nonfatal thromboembolic stroke, and progressive heart failure and death. Therefore, knowledge of the incidence and optimal identification of an apical outpouching seem to be important for counseling patients on the expected risks of their disease. However, it was not clear whether the prognosis was based on the presence of the aneurysm or any form of apical wall motion abnormality or was related to the ApHCM itself.
We examined the echocardiographic features of all patients with ApHCM seen in our HCM clinic, to study the prevalence and clinical correlates of apical outpouching in this population.
Methods
Study Population
We present a retrospective review of patients, identified through the HCM database at the Mayo Clinic (Rochester, MN), with the diagnosis of ApHCM and seen between June 1, 1976, and September 30, 2006. Two hundred ten patients with the initial diagnosis of ApHCM, representing 7.9% of the 2,662 patients referred to the HCM clinic at Mayo Clinic during this interval, were identified.
All patient charts were analyzed, and the most recent echocardiographic study was reviewed. A diagnosis of ApHCM was based on the predominant hypertrophy of apical LV myocardium of >12 mm distal to the papillary muscles. After reviewing the echocardiographic studies, we excluded 17 patients from this study for the following reasons: criteria for ApHCM not fulfilled (9 patients) or diagnosis compatible with isolated LV noncompaction (3 patients), endocardial fibroelastosis (3 patients), restrictive cardiomyopathy (1 patient), and pheochromocytoma (1 patient), leaving 193 patients in the study cohort.
Clinical data, electrocardiograms, and echocardiographic reports and images were reviewed. The data collected were age, sex, patient history that included symptoms (i.e., angina, palpitations, syncope, dyspnea, and functional class), coronary risk factors, arrhythmia data, electrocardiographic data, and coronary angiography, as well as cardiac magnetic resonance imaging (MRI) data when available.
The study was approved by the Mayo Clinic Institutional Review Board.
Analysis of Echocardiography
Complete two-dimensional and Doppler echocardiographic examinations were performed in all patients in accordance with the recommendations of the American Society of Echocardiography. LV biplane ejection fraction was estimated or measured. The echocardiographic features analyzed for this study were septal wall thickness, posterior wall thickness, maximal LV wall thickness of an apical segment, LV ejection fraction, and left atrial dilatation (by M-mode or left atrial volume index). For left atrial dilatation by M-mode echocardiography, dilatation was defined as >3.8 cm in women and >4 cm in men at end-systole; left atrial volume index was defined as >28 mL/m 2 of body surface area. Systolic pulmonary artery pressure was estimated on the basis of the systolic pressure difference between the right ventricle and right atrium measured by continuous-wave Doppler echocardiography plus the estimated right atrial pressure on the basis of the diameter and respiratory variability of the diameter of the inferior vena cava.
The most recent complete echocardiographic examination stored on videotape or acquired in digital format was reviewed, focusing on regional wall motion of the apex and the presence of an apical outpouching, and wall thickness was measured. Apical outpouching was defined as persistent apical cavity in which the apical cavity dimension at end-systole was greater than in the midventricular cavity dimension at end-systole. Apical aneurysm was defined as a discrete, thin-walled dyskinetic or akinetic segment of the most distal portion of the chamber, with a relatively wide communication to the LV cavity. Maximal apical wall thickness at end-diastole was measured when possible; a measurement of <13 mm was considered normal. The presence or absence of a gradient in the midventricular/apical region (late peaking maximal systolic gradient or maximal early diastolic gradient) was noted. An early diastolic gradient was defined as a velocity gradient between apex and base during isovolumic relaxation time caused by a delay of diastole at the apical level and transiently higher pressure at the apex.
Sustained cavity obliteration was defined as systolic cavity obliteration persisting up to at least early diastole.
Contrast echocardiography (mostly using perflutren protein type A microspheres injectable suspension [Optison; GE Healthcare, Fairfield, CT]) has been used since 1996. An intravenous dose of 0.2 mL of the contrast agent was injected, followed by a saline flush until sufficient contrast was seen opacifying the LV apex. Contrast echocardiography was used in 78 patients (40%).
Additional Cardiac Imaging
Cardiac catheterization was performed in 105 patients (54%). Coronary artery disease was defined as coronary artery stenosis of ≥50% observed with cardiac catheterization and selective coronary angiography. Nuclear perfusion imaging was performed in 53 patients (27%). In 30 patients (16%), cardiac MRI was performed.
Electrocardiographic Analysis
The most recent standard 12-lead electrocardiograms were reviewed for the 176 patients for whom they were available. Heart rate and rhythm were recorded. QRS duration, QT interval, and corrected QT (QTc) interval were measured. A QTc interval > 470 msec in men and > 480 msec in women was regarded as abnormally prolonged unless left bundle branch block was present (three patients). The presence and absence of and the number of leads with negative T waves in the anterior leads were noted. Atrial and ventricular arrhythmia history was obtained from the clinical history, electrocardiography, and Holter recordings.
Statistical Analysis
Descriptive statistics include frequencies and percentages for categorical data and mean ± SD for continuous data. Pearson’s χ 2 tests or Fisher’s exact tests were used to compare categorical data between the groups with and without apical outpouching, as appropriate. Two-sample t tests or Wilcoxon’s rank-sum tests were used to compare continuous data between the groups. P values < .05 were considered statistically significant. Survival was analyzed with use of Kaplan-Meier methods, and comparisons between groups were done using the log-rank test statistic. For this analysis, data of patients were censored at the time the patients were last known to be alive. Data were analyzed using StatView for Windows version 5.0 and SAS version 9.1 (SAS Institute Inc., Cary, NC).
Results
Clinical and Demographic Features
Clinical characteristics of the patients are shown in Table 1 . In this study cohort of 193 patients with ApHCM, 29 patients (15%) had apical outpouching, including 6 patients with apical aneurysms. Findings of the 29 patients with apical outpouching ( Figures 1 to 3 and Videos 1 to 4 (view video clips online) show a case example of ApHCM) were compared with those without apical outpouching (164 patients [85%]). A family history of sudden cardiac death was more common in patients with apical outpouching, who also tended to be more symptomatic on the basis of functional class, than patients without apical outpouching ( P = .02). There was no difference in documented coronary artery disease or standard coronary artery disease risk factors. The presence of an apical outpouching was not related to the patient’s age at diagnosis ( P = .99).
| Characteristic | Patients | P | ||
|---|---|---|---|---|
| All ( n = 193) | With apical outpouching ( n = 29) | With no apical outpouching ( n = 164) | ||
| Men | 120 (62%) | 18 (62%) | 102 (62%) | .99 |
| Age at echocardiographic examination (y) | 61 ± 17 | 64 ± 15 | 60 ± 17 | .34 |
| Family history of HCM | 31 (16%) | 4 (14%) | 27 (16%) | .72 |
| Family history of SCD | 19 (10%) | 6 (21%) | 13 (8%) | .04 |
| Arterial hypertension | 102 (53%) | 13 (45%) | 89 (54%) | .35 |
| Dyspnea on exertion | 117 (61%) | 17 (59%) | 100 (61%) | .81 |
| Angina | 45 (23%) | 11 (38%) | 34 (21%) | .06 |
| NYHA functional class | .02 | |||
| I | 98 (51%) | 9 (31%) | 85 (52%) | |
| II | 55 (28%) | 10 (34%) | 45 (27%) | |
| III or IV | 40 (21%) | 10 (34%) | 30 (18%) | |
| Coronary artery disease | 40 (21%) | 7 (24%) | 33 (20%) | .62 |
| Syncope | 28 (15%) | 3 (10%) | 25 (15%) | .49 |
| Heart failure | 35 (18%) | 5 (17%) | 30 (18%) | .89 |
| Stroke | 22 (11%) | 3 (10%) | 19 (12%) | .85 |
Echocardiographic Features
Echocardiographic findings are shown in Table 2 . Maximal apical wall thickness was 20 ± 5 mm and was greater among patients with apical outpouching ( P = .01). Hypertrophy that started at the level of the midventricular papillary muscle, often including papillary muscle hypertrophy or apical displacement of the papillary muscle, was present in 120 patients. Sustained cavity obliteration, assessed with two-dimensional echocardiography, tended to occur more often in patients with apical outpouching ( P = .05). Otherwise, there was no baseline difference between the two groups of patients. In 2 patients (7%), the apical outpouching was transient.
| Echocardiographic finding | Patients | P | ||
|---|---|---|---|---|
| All ( n = 193) | With apical outpouching ( n = 29) | With no apical outpouching ( n = 164) | ||
| LVEDD (mm) ( n = 156) | 48 ± 6 | 50 ± 6 | 48 ± 6 | .09 |
| Basal septal wall thickness (mm) ( n = 160) | 15 ± 5 | 13 ± 4 | 15 ± 5 | .13 |
| Basal posterior wall thickness (mm) ( n = 152) | 12 ± 3 | 11 ± 2 | 12 ± 30 | .29 |
| Maximal apical wall thickness (mm) ( n = 177) | 20 ± 5 | 22 ± 5 | 19 ± 5 | .01 |
| LV ejection fraction (%) | 67 ± 9 | 67 ± 9 | 67 ± 9 | .75 |
| Abnormal diastolic function ( n = 125) | 95 (76%) | 19 (83%) | 76 (75%) | .41 |
| Left atrial dilatation ( n = 186) | 133 (72%) | 21 (72%) | 112 (71%) | .91 |
| Sustained cavity obliteration | 66 (34%) | 5 (17%) | 61 (37%) | .05 |
| Estimated systolic PAP (mm Hg) ( n = 125) | 41 ± 15 | 41 ± 20 | 41 ± 14 | .59 |
| LV systolic apical gradient ( n = 186) | 75 (40%) | 16 (57%) | 59 (37%) | .06 |
| LV diastolic gradient ( n = 186) | 27 (15%) | 11 (39%) | 16 (10%) | <.001 |
| LVH starting at midventricular level | 120 (62%) | 12 (41%) | 108 (66%) | .02 |
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