The Analytical Effect of Patient Selection Biases

Bacgond The clinical significance of exercise-induced chest pain remains controversial, as reflected by sharply discordant clinical results within the medical literature. Thus, we developed a prospective study to compare the functional significance of silent versus symptomatic ischemia and to evaluate whether patient selection biases influence this analysis. Metds andRss We evaluated 117 patients (mean age, 63±9 years) with ischemic ST-segment depression during treadmill testing. Each patient underwent T1-201 myocardial perfusion single-photon emission computed tomography (SPECT) after exercise followed by 24-ambulatory ECG monitoring. Patients were divided into silent versus symptomatic cohorts and were compared for the degree of hemodynamic, exercise and ambulatory ECG, and thallium abnormalities during stress testing. Analyses were repeated as the patient population became increasingly restricted. Compared with the silent patients, patients with chest pain during exercise had a shorter exercise duration (P<.009), lower peak heart rate (P=.009) and double product (P=.005), lower heart rate threshold for ST depression (P<.05), more episodes of ambulatory ST-segment depression (P<.05), a higher fre-