Significance of Magnetic Resonance Imaging in Apical Hypertrophic Cardiomyopathy




Apical hypertrophic cardiomyopathy (HC) is an uncommon variant of nonobstructive HC with peculiar characteristics. The investigators report a series of 13 consecutive Caucasian patients with a suspicion or diagnosis of apical HC on the basis of electrocardiographic and/or echocardiographic findings who prospectively underwent magnetic resonance imaging with late gadolinium enhancement (LGE) evaluation. All but 1 patient presented T-wave inversion in the anterolateral leads on electrocardiogram, with a mean maximum negative T wave of 7.0 ± 3.9 mm. Echocardiography provided correct diagnoses in 9/13 patients (69%), while in 4 patients echocardiographic results were normal or inconclusive. Magnetic resonance imaging showed a spadelike morphology of the left ventricle in 6 patients and identified an apical aneurysm in 4. Eleven patients (85%) presented LGE with a mean percentage of 2.3 ± 2.6% of total left ventricular mass. In 9 (69%) patients LGE was limited to the hypertrophic segments while in 6 (46%) patients it was also present in nonhypertrophic segments. In conclusion, magnetic resonance imaging in patients with apical HC showed a high incidence of apical aneurysms and a peculiar distribution of LGE, that was not limited to hypertrophic segments.


Apical hypertrophic cardiomyopathy (HC) is a subtype of HC in which myocardial hypertrophy predominantly involves the apex of the left ventricle. Apical HC has a peculiar geographic distribution, being a common morphologic expression of the disease in Asian countries but relatively rare in Western populations. Apical HC usually has a low rate of cardiovascular mortality, but severe clinical manifestations, including arrhythmias and myocardial infarction with segmental aneurysm formation, have been increasingly reported. Conventionally, transthoracic echocardiography is used for the diagnosis of HC, but diagnostic accuracy for the identification of hypertrophy confined to the left ventricular (LV) apex is limited without using contrast echocardiography or 3-dimensional echocardiography. In recent years, cardiac magnetic resonance imaging (MRI) has emerged as an excellent tool for evaluating cardiac morphology and function and for tissue characterization. Only a few series of patients have been published on cardiac MRI in apical HC (especially in the Caucasian population), reporting the presence of late gadolinium enhancement (LGE) in almost 50% of patients, limited mainly to the hypertrophic apical segments. We report our series of 13 patients.


Methods


Thirteen consecutive patients with a suspicion or diagnosis of apical HC on the basis of electrocardiographic and/or echocardiographic findings were prospectively studied with MRI. The diagnosis of spadelike apical HC was based on the published criteria, which include an apical wall thickness ≥15 mm, a ratio ≥1.3 of anterior LV short-axis end-diastolic thickness at the apical level to the basal level, and the presence of spadelike morphology on visual inspection of MRI long-axis images by 2 independent observers (RF, LL). Nonspadelike apical HC was diagnosed when spadelike morphology was not present but the maximum apical LV thickness was ≥15 mm and the ratio of maximum apical thickness to maximum basal thickness was ≥1.3. Four-chamber and 2-chamber images were also assessed for the presence of apical cavity obliteration and a spadelike systolic cavity configuration. LV 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.


MRI was performed using a 1.5-T scanner (Signa Twin Speed Excite; GE Medical Systems, Milwaukee, Wisconsin) with surface coils and prospective electrocardiographic triggering. LV end-systolic and end-diastolic diameters and volumes, LV end-diastolic mass, and maximal (end-diastolic) wall thickness were traced and recorded from the short-axis and long-axis views (8 mm slice thickness, no gap) of the standard electrocardiographic-gated steady-state free precession cine sequence. Image parameters were a repetition time of 3.5 ms, an echo time of 1.6 ms, temporal resolution of 40 ms, a matrix size of 224 × 160, a flip angle of 45°, bandwidth of 125 kHz, and 8 to 16 views per segment. If necessary, the long-axis views were repeated to ensure that the slice passed precisely through the distal apex and fully appreciated the cavity, even when the cavity was almost obliterated. Myocardial LGE images for the detection of hyperenhancement were obtained approximately 10 minute after the intravenous injection of gadopentate dimeglumine 0.2 mmol/kg (Magnevist; Schering AG, Berlin, Germany) using a segmented inversion recovery fast gradient-echo sequence in the short-axis plane of the left ventricle and in the long-axis view, with 9 mm slice thickness and no gap. Image parameters were a repetition time of 5.3 ms, an echo time of 1.3 ms, a flip angle of 20°, a matrix size of 256 × 160, 2 signals acquired, and a field of view of 320 mm. Optimal inversion time to null the normal myocardial signal was determined for each patient. Areas of hyperenhancement were traced manually and quantified using specific software (ReportCard; GE Medical Systems) as percentage of LV mass. The threshold of signal intensity above which LGE was considered to be present was that of the mean signal intensity of healthy myocardium plus 2 SDs.


Data are expressed as mean ± SD. Spearman’s ρ correlation was used for comparing continuous variables, and p values ≤0.05 were considered statistically significant.




Results


Our study population consisted of 13 consecutive Caucasian patients (8 men, mean age 55 ± 14 years) with a diagnosis or suspicion of apical HC ( Table 1 ). All patients were referred to our center to undergo echocardiography to investigate an abnormal electrocardiogram. All but 1 patient presented electrocardiographic alterations of the ventricular repolarization in the anterolateral leads in the form of T-wave inversion, with a mean maximum negative T wave of 7.0 ± 3.9 mm. One patient (patient 9) presented complete right bundle branch block. Nine patients (69%) presented giant negative T waves (≥5 mm). Echocardiography provided a diagnosis of apical HC in 9 out of 13 patients (69%) while in 4 patients, echocardiography was normal or inconclusive (31%). Three patients (23%) had a family history of HC and 1 had a family history of sudden death. Twelve patients were completely asymptomatic (92%). Only 1 (patient 10, Table 1 ) reported shortness of breath (New York Heart Association functional class II) and chest discomfort during paroxysmal supraventricular tachycardia (recorded on a Holter monitor), however these symptoms disappeared after starting β blockers. On MRI, the mean LV mass was 72 ± 16 g/m 2 and the mean maximum apical thickness was 19 ± 3 mm. Six patients presented a spadelike morphology of the left ventricle. In 4 patients apical aneurysms were identified ( Figure 1 ). Eleven patients showed LGE, with a median percentage of 1.4% (interquartile range 0.2% to 3.1%) of total LV mass. Nine patients showed LGE in hypertrophic segments while 6 (46%) also presented LGE in nonhypertrophic segments, especially in basal and midcavity antero- and inferoseptal segments or at the interventricular junction level ( Figure 2 ).



Table 1

Demographic, electrocardiographic, and magnetic resonance imaging characteristics of the study population






















































































































































































































Patient Age (years) Gender Family History of HC NYHA Class Maximal T-Wave Inversion on ECG (mm) Maximum Apical Thickness (mm) a/b Ratio LV Mass (g/m 2 ) Spadelike Morphology Apical Aneurysm Hypertrophic Segments With LGE Non-hypertrophic Segments With LGE LGE % of LV Mass
1 23 F 0 1 2 18 1.8 84 0 0 0
2 44 M + 1 0 19 1.4 85 0 0 12, 13, 16 1.4
3 45 M 0 1 8 19 2.1 100 0 0 14, 15 9, 10 1.3
4 49 M 0 1 11 15 1.4 76 0 + 17 0.3
5 51 M 0 1 9 17 1.5 59 0 + 0
6 51 M 0 1 3 21 1.7 84 + 0 13, 15, 17 8 3.1
7 57 M 0 1 8 21 2.1 90 + 0 14 0.2
8 57 F + 1 6 27 5.8 54 + + 13, 14, 15 1, 2, 8 6.5
9 64 M 0 1 13 22 2.7 83 0 0 11, 13, 14, 15, 16, 17 1, 3, 5 7.1
10 66 M + 2 4 17 1.6 57 + 0 13, 15 3, 9 2.2
11 70 F 0 1 12 18 2.2 58 + 0 2, 3, 8, 9 2.1
12 73 F 0 1 7 16 1.5 58 + 0 0
13 74 F 0 2 9 16 2.0 53 0 + 13, 14, 15, 16, 17 6.2

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Dec 23, 2016 | Posted by in CARDIOLOGY | Comments Off on Significance of Magnetic Resonance Imaging in Apical Hypertrophic Cardiomyopathy
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