Regional thallium-201 washout and myocardial hypertrophy in hypertrophic cardiomyopathy and its relation to exertional chest pain.

The mechanism of exertional chest pain in hypertrophic cardiomyopathy is uncertain, but may relate to myocardial ischemia. To study the mechanism of exertional chest pain in hypertrophic cardiomyopathy, dipyridamole-stress thallium-201 single-photon emission computed tomography was performed in 82 consecutive patients, and the 3-hour washout of thallium in relation to the tomographic image, regional wall thickness on echocardiography, and other clinical findings was analyzed. There was a weak inverse correlation of regional washout and wall thickness in 298 analyzed quadrant areas (r = -0.29; p = 0.0001). Twenty-five patients (31%) had history of exertional chest pain, and showed a significantly lower total washout and greater maximal left ventricular wall thickness than did those without chest pain (32 +/- 10% vs 37 +/- 9% [p = 0.03], and 27 +/- 7 vs 23 +/- 7 mm [p = 0.03], respectively). Even in mildly and nonhypertrophied areas, patients with chest pain had a significantly lower regional washout than did those without pain (33 +/- 10% vs 38 +/- 9%; p = 0.02), despite similar left ventricular wall thickness (12 +/- 2 vs 11 +/- 3 mm; p = NS). Reduced washout was strongly associated with exertional chest pain and was observed in myocardial regions that had normal as well as increased thickness, which indicates that this abnormality of thallium kinetics is a function of the disease process and not the magnitude of left ventricular hypertrophy.