Geometric assessment of asymmetric septal hypertrophic cardiomyopathy by CMR.
OBJECTIVE
The aim of this study was to analyze the geometric pattern of hypertrophy (HT) in patients with asymmetrical septal hypertrophic cardiomyopathy (HCM) using cardiac magnetic resonance (CMR) and to test the hypothesis that at least in some patients, the HT follows a longitudinal spiral pattern.


BACKGROUND
The highly heterogeneous phenotypic expression of HCM is a well-known phenomenon. CMR has emerged as a robust 3-dimensional (3D) tomographic imaging technique that is increasingly used to explore phenotypic expression.


METHODS
Short-axis cine CMR was used to study the 3D extent of HT (i.e., radial, circumferential, and longitudinal extent, as well as the relation between circumferential and longitudinal extent). Inclusion criteria were septal wall thickness (WT) ≥15 mm and septal to free wall WT ratio >1.3.


RESULTS
CMR was performed in 132 patients. Maximal WT was 22 ± 5 mm, with a circumferential extent of 131 ± 51°, and a longitudinal extent of 64 ± 19%, resulting in a hypertrophied left ventricular (LV) surface of 26 ± 15%. Linear regression analysis showed in 86% of patients a consistent course of HT along the longitudinal direction. The HT invariably started at the basal anteroseptum and rotated, except in 2 patients, in a counterclockwise direction (CC-spiral patients) with a mean global rotation of 116 ± 68° (range 5° to 350°). After the CC-spiral patients were divided according to magnitude of rotation quartiles (Q1: 5° to 70°, Q2: 75° to 105°, Q3: 110° to 150°, and Q4: 155° to 350°), Q4 patients were significantly older and had more LV outflow tract obstruction and hypertension than patients without the spiraling pattern. In 11 patients, continuation of HT into an apical form of HCM was found.


CONCLUSIONS
Using 3D analysis, we found that the majority of patients with asymmetrical septal HCM in fact showed a spiral pattern of HT following a counterclockwise (or "left-handed") spiral trajectory. The variation in magnitude of rotation among patients, however, was highly variable. Further research is warranted to better understand the significance of the current findings, in particular to relate them to the genetic and morphological substrate, hemodynamic consequences, and patient outcome.
Department of Radiology, UZ Leuven, Leuven, Belgium.
Anca
A
Florian
Pier Giorgio
PG
Masci
Stijn
S
De Buck
Giovanni Donato
GD
Aquaro
Piet
P
Claus
Giancarlo
G
Todiere
Johan
J
Van Cleemput
Massimo
M
Lombardi
Jan
J
Bogaert
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001530:Belgium; D002312:Cardiomyopathy, Hypertrophic / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D016009:Chi-Square Distribution; D018450:Disease Progression; D005260:Female; D020022:Genetic Predisposition to Disease; D006346:Heart Septum / Q000473:pathology*; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007558:Italy; D016014:Linear Models; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D013318:Stroke Volume; D016277:Ventricular Function, Left; D055815:Young Adult