MRI and cine MRI of asymmetric septal hypertrophic cardiomyopathy.

OBJECTIVE

This study was designed to determine MR and cine MR characteristics of asymmetric septal hypertrophic cardiomyopathy and to correlate MR and cine MR features with the severity of left ventricular outflow tract obstruction.

MATERIALS AND METHODS

Ten consecutive patients with asymmetric septal hypertrophic cardiomyopathy [resting obstructive (n = 3), latent obstructive (n = 4), nonobstructive hypertrophic (n = 3)] and five healthy volunteers underwent MRI and cine MRI. Oblique two chamber and four chamber views were obtained in all cases.

RESULTS

In the 10 patients, the mean +/- SD end-diastolic myocardial thickness was 22.7 +/- 6.3 mm in the basal septum and 13 +/- 3.9 mm in the posterolateral wall with a ratio of 1.76 +/- 0.30; the corresponding values were 10.6 +/- 1.1, 10.4 +/- 1.1, and 1.02 +/- 0.08 mm, respectively, in five healthy volunteers. The mean systolic thickening of the basal septum was 22 +/- 12%. This value was 49 +/- 4% in the five healthy volunteers. In resting obstructive hypertrophic cardiomyopathy, septal wall thickness was > or = 25 mm with a systolic thickening of 10%. A systolic anterior motion of the mitral valve was demonstrated in four patients with resting subaortic pressure gradients ranging from 28 to 120 mm Hg. A signal void area was demonstrated within the left ventricular outflow tract during systole in the seven patients with obstructive cardiomyopathy. This signal void area reached its maximum during early systole in the most severe obstructions and during midsystole in the less severe obstructions.

CONCLUSION

In patients with asymmetric septal hypertrophic cardiomyopathy, gross correlation was demonstrated between severity of obstruction and several MR and cine MR features including increased end-diastolic thickness of the septal wall, decreased systolic thickening of the septal wall, systolic anterior motion of the mitral valve, and signal void area within the left ventricular outflow tract during systole.