Results:
Baseline characteristics and predictors of hypertensive response:Tables 1 and 2 summarize the baseline patient characteristics of all patients and as a function of presence or absence of a hypertensive response to dobutamine. The mean age was 59+ 12 years, 45% were women, 71% had diabetes mellitus. Of the 249 patients 53 (21%) had a hypertensive response.
As shown in table 2, hypertensive response was predicted principally by higher baseline systolic blood pressure (p<0.0001). They also had higher estimated left atrial pressure (p=0.02) with similar prevalence of right atrial hypertension by size of inferior vena cava as well as by physical examination. They were more likely to be on angiotensin converting enzyme inhibitor or receptor blocker (p=0.01) and had a trend towards larger number of anti-hypertensive medications (p=0.06). Left atrial enlargement and LV hypertrophy were more frequent in the hypertensive group (p=0.006 and p=0.01 respectively). On multivariable analysis, only pre-stress systolic blood pressure was a predictor of hypertensive response (p<0.0001). A graded relationship between pre-stress systolic blood pressure and hypertensive response was observed (table 3). A pre-stress systolic blood pressure of 160 or more was highly predictive of hypertensive response during dobutamine stress (Table 3). Pre-stress diastolic blood pressure was not predictive of stress induced hypertensive response.
Stress test positivity and their angiographic correlates:Hypertensive response resulted in far more peak stress wall motion abnormalities than normotensive group patients (OR 2.75, 95% CI 1.44-5.24, P = 0.002). As shown in figure 1, 25 (47%) of the 53 patients with hypertensive response had stress induced wall motion abnormalities; of these 22 patients underwent coronary angiography and 12 (54%) were abnormal. Additionally, 12 of the 28 patients from hypertensive group without systolic wall motion abnormalities were also referred for coronary angiography and 7 (58%) were positive for significant coronary artery disease. Even though some patients had normal dobutamine stress echo, they underwent coronary angiography because of request by the transplant committee.
In the normotensive response group (n= 196), only 48 (24%) patients had stress induced wall motion abnormalities; of these 42 underwent coronary angiography and 18 (43%) had significant CAD. In addition, 75 patients from normotensive group without stress induced wall motion abnormalities also received coronary angiography on the request of the transplant committee and 22 (29%) had significant CAD. Thus, the sensitivity of dobutamine stress test in normotensive group was 46% and specificity was 66% (table 4).
Prognostic implications: Hypertensive response during stress test was not predictive of mortality over the duration of follow-up (Figure 2). Stress induced wall motion abnormalities were predictive of higher mortality in the normotensive group (p=0.03), but not in the hypertensive group (Figure 3).