Exercise Testing in Subjects with Aortic Stenosis
Although studies have delineated possible mechanisms for effort syncope in aortic stenosis, a review of the literature (Thble 1) demonstrates rare complications from exercise testing when performed with appropriate caution and monitoring. Although used predominantly in pediatric cardiology to assess congenital aortic stenosis and the need for surgical therapy, exercise testing has more recently been performed in adults to resolve disparities between history and clinical findings. With the advent of Doppler echocardiography, asymptomatic aortic stenosis in the elderly has become a challenging therapeutic decision. Glew et al reviewed eight cases of sudden death due to congenital aortic stenosis and stressed its rarity and the importance of warning symptoms. In addition, they recommended that invasive evaluation be performed in the presence of symptoms, narrowed peripheral arterial pulses, or evidence on the electrocardiogram of left ventricular strain. They noted that rarely did patients with normal electrocardiograms die suddenly.
Exercise testing has been reported in children with valvular stenosis to distinguish noninvasively those patients who would benefit from surgery. However, these studies were performed before use of Doppler echocardiography was widespread. The approach to the asymptomatic child with aortic stenosis remains perplexing. canadian neighborhood pharmacy
Early studies in pediatric patients were concerned with decision-making and predicting the severity of AS. Halloran studied 31 children with congenital aortic stenosis using bicycle exercise at a workload sufficient to raise the heart rate to at least 170 beats/ min. She noted that all 15 children with gradients of 60 mm Hg or greater had 2 mm or more ST depression in V5. In only one subject of 16 with gradients less than 50 mm Hg was 2 mm ST depression present Likewise, Chandramouli et al noted that among 44 children with AS, 1 mm ST depression predicted a gradient of at least 54 mm Hg, and only one subject without significant ST depression had a gradient of 52 mm Hg. Neither of these studies evaluated blood pressure response or exercise capacity. Kveselis et al also noted gradients of greater than 35 mm Hg in children with significant ST depression and suggested that ST depression was more related to the left ventricular oxygen supply-demand ratio. They also observed that two of 12 children with gradients greater than 35 mm Hg had a fell in blood pressure. Barton et al demonstrated that in addition to ST depression, a systolic blood pressure increase of less than 30 mm Hg was predictive of at least a 50 mm gradient.
Table 1—Summary of Nine Studies of Exercise Testing in Aortic Stenosis
|Mean age||(8-17)||(5-19)||(35-56)||11||12||12 (6–20)||46±5||13 ±3||58±14||65 (52-78)|
|Mean value area (cm2)||1.22±.74||•||•||•||*||•||1.0±.6||.60±.16||•||(.48-1.63)|
|Mean valve gradient||16<50||(10–112)||(53-80)||86 (30-235)||(<30 to <70)|
|(mm Hg)||15>50||38 (14-80)||•||59 ±18||57 ±23||(18-64)|
|Maximal heart rate|
|Exercise capacity||•||*||*||1702 kg/m t||(3,996-5,893 Kg/m)t||•||520 kg/min||800 kg/min||500 kg/min||•|
|>1.0 mm ST depression||48%||27%||37%||(71-100%)||(38-89%)||54%||*||100%||X-1.33±.8|
|Blood pressure response||*||*||*||*||(0-32%)||63%||*||58%|