Differential effects of dobutamine versus treadmill exercise on left ventricular volume and wall stress.

BACKGROUND: Dobutamine and exercise echocardiography are well-validated modalities used for the evaluation of patients with suspected myocardial ischemia. Patients undergoing dobutamine stress echocardiography (DSE), however, experience less angina, ST-segment depressions, and wall motion abnormalities. Other than the effect on heart rate, the physiologic and volumetric differences between pharmacologic and exercise-induced stress that affect myocardial oxygen demand are not well defined. The aim of this study was to test the hypothesis that in the absence of ischemia, dobutamine reduces left ventricular (LV) volume, wall tension (WTN), and peak systolic stress (PSS) compared with exercise. METHODS: Seventy patients without ischemia were prospectively enrolled (35 underwent exercise echocardiography and 35 DSE), and various hemodynamic parameters were measured and LV volumes calculated (using the Simpson and Teichholz formulas). Systolic WTN and PSS were determined at rest and stress. RESULTS: LV end-diastolic volume index fell significantly more with dobutamine than with exercise (-34% vs -9%, P < .0001), as did mean end-systolic volume index (-55% vs -37%, P = .07). Systolic blood pressure increased more with exercise (41 ± 22 vs 1 ± 33 mm Hg, P < .0001), as did cardiac index (2.5 ± 0.7 vs 1.0 ± 0.8 L/min/m(2), P < .0001). Systolic WTN increased with exercise by 24% (P < .0001) but decreased with dobutamine by 18% (P < .0001). PSS increased with exercise by 21% (P < .0001) but decreased with dobutamine by 23% (P < .0001). CONCLUSIONS: The degree of stress achieved with DSE appears to be considerably different than with exercise. DSE produces greater reductions in LV end-diastolic and end-systolic volumes than exercise and decreases rather than increases in WTN and PSS. The lower WTN and PSS were related to both a decrease in LV volume and lower systolic blood pressure with dobutamine. These observations support recommendations favoring exercise stress testing in patients able to exercise and reinforce the notion that high-risk echocardiographic features of ischemia such as stress-induced LV dilatation may be less striking or absent with DSE.

Very large incidental pericardial effusion attributable to minoxidil: resolution without drainage.

We present a case of drug-induced pericardial effusion in a patient with end-stage renal disease. Hypertension is frequent among patients with chronic renal failure and sometimes it is necessary to use agents, like minoxidil. Many papers have reported the association between minoxidil and pericardial effusion, both in dialysis patients and those with normal renal function. These effusions sometimes require drainage because of tamponade, but usually disappear after discontinuation of the drug, which is what happened in our patient. In any patient on dialysis treated with minoxidil, the appearance of pericardial effusion unresponsive to ultrafiltration should launch the suspicion of this complication and the drug should be withdrawn.

Prevalence and clinical characteristics of nondilated cardiomyopathy and the effect of atrial fibrillation.

The treatment of patients with chronic heart failure and those with asymptomatic left ventricular (LV) dysfunction has focused primarily on patients with LV enlargement and a low ejection fraction (EF). Little attention has been paid to those with a normal chamber size and a low EF. We sought to examine the LV geometry and clinical characteristics in such patients with nondilated cardiomyopathy. Of 3,350 transthoracic echocardiograms performed during a 6-month period, 696 showed an EF of < or =0.45. The patients with an end-diastolic diameter of >56 mm, regional wall motion abnormalities, or valvular disease were excluded. Of the 696 patients, 98 met these criteria, and their medical records were reviewed. The average age was 71 +/- 14 years, and 56% were men. Common co-morbidities included hypertension in 52% and atrial fibrillation (AF) in 43%. Only 22% had disabling cardiac symptoms (functional class III or greater). The average end-diastolic dimension was 49 +/- 5 mm, and the EF was 34 +/- 8%. LV hypertrophic remodeling was present in 53%. A second echocardiogram (422 +/- 177 days after the baseline study) was available for 54 patients. The chamber size was unchanged, but the EF had increased from 33 +/- 8% to 40 +/- 14% (p <0.01). The improvement in EF was seen in the group with AF (33 +/- 6% to 44 +/- 15%, p <0.01) but not in those with normal sinus rhythm (33 +/- 9% to 37 +/- 12%, p = NS). In conclusion, 14% of patients with an EF of < or =0.45 had nondilated cardiomyopathy, often with LV hypertrophic remodeling and/or AF. An improvement in LV function can be expected in many patients with nondilated cardiomyopathy, particularly those with AF.

Cardiac events in patients with negative maximal versus negative submaximal dobutamine echocardiograms undergoing noncardiac surgery: importance of resting wall motion abnormalities.

OBJECTIVES: This study sought to evaluate the negative predictive value (NPV) of preoperative dobutamine stress echocardiography (DSE) in patients who fail to achieve target heart rate (HR) and assess the influence of resting wall motion abnormalities (WMAs) without demonstrable ischemia on perioperative events. BACKGROUND: The prognostic value of a negative-submaximal DSE study before noncardiac surgery is unknown. METHODS: Consecutive patients (n = 429) who underwent surgery over a three-year period, preceded by DSE, were included. We compared perioperative event rates among those without inducible ischemia according to whether or not 85% age-adjusted maximum HR was achieved, and whether WMAs were present at rest. RESULTS: Of 397 negative DSEs, peak HR was <85% maximum predicted in 62 (16%). Most were receiving beta-blockers (77%). The average dobutamine and atropine doses were 48 microg/kg/min and 1.2 mg, respectively. Average HR was 115 beats/min (74% maximum predicted). Perioperative myocardial infarctions occurred more frequently in patients with positive tests (3 of 32 [9.4%] vs. 7 of 397 [1.8%]; p = 0.03), but with similar frequency among the negative-maximal and negative-submaximal groups (6 of 335, 1.8% vs. 1 of 62, 1.6%, respectively). Accordingly, the NPV was 98% in both subgroups. Events occurred exclusively in patients with WMAs at rest: 7 of 100 (7%) versus 0 of 297 (0%) (p < 0.0001). CONCLUSIONS: In patients undergoing preoperative DSE, failure to achieve target HR is not uncommon despite an aggressive DSE regimen. A negative DSE without resting WMAs has excellent NPV regardless of the HR achieved. Patients with resting WMAs appear to be at increased risk for perioperative events even without provokable ischemia.

Paradoxical embolism in the left main coronary artery: diagnosis by transesophageal echocardiography.

We describe a patient with a paradoxical coronary embolism diagnosed by transesophageal echocardiography. The patient developed a stroke followed by a myocardial infarction. Coronary angiography showed an obstruction of the left main coronary artery. Transesophageal echocardiography showed the mechanism of the neurologic and cardiac events to be a paradoxical embolism. Emergency surgical retrieval of the thrombus lodged in the left main coronary ostium and of a separate thrombus traversing a patent foramen ovale was performed. To our knowledge, direct visualization of the paradoxical coronary embolism by echocardiography has not been reported previously. We discuss mechanisms responsible for paradoxical coronary embolism and review the literature pertaining to this condition.