Stress-induced changes in subendocardial tissue texture in hypertrophic cardiomyopathy: An echocardiographic videodensitometric study

Background: Myocardial ischemia changes myocardial acoustic properties, inducing increase of integrated backscatter and blunting of cyclic variation of backscatter. Stress-induced subendocardial underperfusion has been demonstrated in patients with hypertrophic cardiomyopathy (HCM). Aim: To evaluate the potential of a videodensitometric approach in assessing transmural ultrasonic tissue changes in HCM during dipyridamole infusion. Methods: Twenty-two patients (13 males, 50 +/- 12 years) with HCM underwent dipyridamole echo testing (DET). Myocardial gray levels amplitude was calculated off-line on digitized images in the left subendocardial (LV-endo), right subendocardial (RV-endo) region of the interventricular septum and posterior wall (long axis parasternal view). Results: The thickness of the interventricular septum and posterior wall was 1.9 +/- 0.3 and 1.17 +/- 2.1 cm, respectively. In the LV-endo layer, the cyclic variation was blunted during DET (rest = 37 +/- 14 vs. DET 27 +/- 20%, p < 0.02). In the RV-endo layer and posterior wall, no changes occurred. In the LV-endo layer of the septum, blunting of cyclic variation was more pronounced in the 10 patients with than in the 12 without ST-segment depression during DET (21.2 +/- 14.7% vs. 43.8 +/- 15.8, p < 0.01). Conclusions: In HCM patients, DET induced blunting of cyclic variation without the evidence of wall motion abnormalities. This reduction was more pronounced when electrocardiographic signs of ischemia were simultaneously elicited by DET.