Graded exercise testing of hypertensive and normotensive subjects : a hemodynamic and electrocardiographic comparison
Szymanski, Linda M.
MetadataShow full item record
It has been proposed that R-wave amplitude (Ramp) changes during exercise may reflect ventricular function and may also aid in the detection of early cardiac involvement in hypertension. The purpose of this study was to determine if Ramp changes during a graded exercise test (GXT) would differentiate between middle-aged hypertensive and normotensive subjects. Subjects included 15 hypertensives (HT), 11 trained normotensives (TR), and 9 untrained normotensives (UT). All subjects underwent a maximal GXT to volitional exhaustion, using the Bruce protocol. HT exhibited higher SBP and DBP at rest and each stage of the GXT (p < .05). RPP was greater at every level (p < .05), except rest and stage 1, in those hypertensives not on beta blockade (HT2; n=9) compared to those on beta blockade (HT1; n=6). RPP in HT2 was greater than both TR and UT at every level (p < .05). RPP in HT2 increased from a resting value of 121.65 to 335.87 in stage 3. Corresponding values in HT1 were 106.15 and 265.22; in TR 82.51 and 241.87; and in UT 98.10 and 289.18. TR exhibited a larger Ramp at rest (x̅ = 20.2 mm) than HT (x̅ = 12.7 mm) and UT (x̅ = 10.6 mm); however, an ANCOVA found all three groups to exhibit a similar Ramp response during exercise (p > .05). Ramp decreased from rest to peak exercise in all groups (p < .05). Values for TR, HT, and UT at peak exercise were 17.1 mm, 11.5 mm, and 9.6 mm, respectively. The effect of electrocardiographic left ventricular hypertrophy (ECG-LVH) on exercise-induced Ramp changes was also investigated. Ramp failed to distinguish between HT with ECG-LVH (HT3, n=5) and HT without ECG-LVH (HT4, n=10). A comparison between HT3 and TR with ECG-LVH (TR1, n=8) also revealed no differences in Ramp response during exercise. In addition, the effect of beta blockade on Ramp was evaluated. Ramp response in HT1 did not differ from HT2 or the other groups (p > .05). Ramp in HT1 decreased from 13.9 mm at rest to 12.4 mm at peak exercise, whereas Ramp in HT2 decreased from 11.9 mm to 10.9 mm. The results of this study do not support the hypothesis that exercise- induced Ramp changes are sensitive indicators of ventricular function. Exercise-induced Ramp changes do not appear helpful in distinguishing hypertensives from normotensives either. In addition, previous findings of Ramp increases during maximal exercise in subjects on beta blockade were not substantiated.