Exercise Testing in Patients with Aortic Stenosis: Subjects with Aortic Stenosis
James et al developed an exercise profile consisting of ST segment depression of 2 mm or more, a decreased systolic blood pressure response of two standard deviations below normal and a decreased total work capacity of two standard deviations below normal. Two or more of these responses occurred predominantly among those with a resting gradient of greater than 70 mm Hg. Because these authors had previously demonstrated a favorable surgical response occurred in patients with a valve gradient of 70 mm Hg or greater, it was suggested that the exercise test offered a safe, noninvasive method for predicting patients with a high gradient.
Whitmer and co-workers obseved a drop in systolic pressure among patients with the highest pressure gradients (greater than 100 mm Hg) and that in five of these seven patients, 3 mm of ST segment depression or greater was observed. Chest pain was common in those with a high gradient, and only in those with gradients greater than 70 mm Hg did symptoms of dizziness develop. After surgery work capacity markedly improved except in those with the most severe gradients. Heart rate remained the same before and after surgery. Exercise-induced ST segment depression returned to normal postoperatively, but took longer to do so among patients with severe aortic stenosis. In patients lacking a normal ST segment response postoperatively, the authors suggested the possibility of residual obstruction or cardiac dysfunction. generic yaz birth control
In adults with AS, Scandinavian cardiologists have reported no complication in over 600 tests. Areskog reviewed 50,000 exercise tests performed in Sweden and reported only two deaths—one of these was a patient with AS. It was concluded that exercise testing is a low-risk procedure which can evaluate exercise capacity, symptoms, evoke signs of hemodynamic compromise, and is a valuable tool for following the course of valvular disease. Linderholm et al have tested over 500 patients with aortic stenosis without any complications. However, no mention was made of the blood pressure response during exercise. A 92 percent predictive accuracy for coronary artery disease was demonstrated in patients with aortic stenosis. The greatest accuracy was obtained using a “coronary insufficiency index score,” expressed in degree of ST depression relative to predicted exercise capacity. This score was surprisingly effective even in patients who had left ventricular hypertrophy and were receiving digitalis. They also looked at an effort-angina score based on its duration, and found no correlation with pressure gradient and a low diagnostic accuracy for coronary artery disease. In contrast, Aronow and Harris safely tested 19 patients with significant aortic stenosis (gradients ranging from 53 to 80 mm Hg) to 90 percent of their maximal predicted heart rate and found significant ST depression in seven patients despite no evidence of hypertrophy. Because of the absence of coronary artery disease they concluded that ST depression was “a functional sign and not an anatomic sign” of limited myocardial perfusion. Al-mendral et al and Nylander et al noted ST segment abnormalities, but did not comment on its relation to coronary artery disease.