Cerebral and ophthalmic artery hemodynamic responses in diabetes mellitus.

OBJECTIVE: To address whether hemodynamic responses in the cerebral arteries and OAs may be altered in patients with diabetic retinopathy. We used TCD to evaluate the effects of changes in BP, posture, and exercise on MCA and OA blood flow velocities. RESEARCH DESIGN AND METHODS: We evaluated 13 patients with BDR, 19 with PDR, and 11 control subjects. Each was tested while supine, breathing 100% oxygen, sitting, and during exercise. RESULTS: Control subjects exhibited linear increases in velocity in the MCA and OA with increases in BP. Those with BDR had higher baseline sBP than control subjects. The MCA velocity response to BP in the BDR group was parallel to, but differed significantly from, the response in control subjects in compensation for the level of BP (ANCOVA F1,53 = 10.1, P = 0.003). The OA velocity response to BP was indistinguishable between the control subjects and the group with BDR. The group with PDR had more elevated BP than control subjects, and those with BDR had more advanced autonomic neuropathy. The PDR group had heterogenous velocity responses in the MCA and OA with respect to BP. None of the control subjects and 3 of 13 of the BDR group had abnormal autoregulatory velocity responses in the MCA or OA to 100% oxygen breathing, whereas 12 of 19 PDR patients were abnormal (P < 0.01). Of those with PDR, 4 had elevated MCA and 3 had elevated OA velocities while supine at rest. CONCLUSIONS: Patients with PDR demonstrated abnormal hemodynamic responses of the cerebral and ophthalmic circulation both at rest and with exercise.

Determination of perioperative cardiac risk by adenosine thallium-201 myocardial imaging.

To determine the predictive value of adenosine thallium-201 myocardial imaging for perioperative cardiac events, 60 consecutive patients referred for preoperative cardiac evaluation were studied before vascular (n = 25), orthopedic (n = 14), or general (n = 21) surgery. Tomographic (n = 52) and planar (n = 8) thallium-201 imaging was performed after adenosine infusion at a rate of 140 micrograms/kg/min for 6 minutes. Two blinded expert observers graded results of adenosine thallium-201 studies as normal (33%), fixed defect only (2%), reversible defect only (48%), and combined (fixed and reversible) defects (17%). After 6 +/- 3 months of follow-up, 81% proceeded to surgery and 43% underwent preoperative coronary angiography. Clinical variables that correlated with perioperative cardiac events were a history of diabetes mellitus (p = 0.05), left bundle branch block (p = 0.02), and left ventricular hypertrophy (p = 0.06) on the resting ECG. This clinically "high-risk" group had an event rate of 22% as compared with no cardiac events in patients in the "low-risk" group without these clinical characteristics (p = 0.005). Stepwise logistic regression analysis revealed that the presence of a combined (fixed and reversible) adenosine thallium-201 defect (p = 0.0007), three-vessel coronary artery disease (p = 0.001), and left bundle branch block (p = 0.02) was predictive of subsequent cardiac events with relative risk ratios of 4.9, 2.9, and 2.2, respectively. Therefore the presence of an adenosine thallium-201 perfusion defect is correlated with and predictive of an increased risk of perioperative cardiac events in patients referred for preoperative risk evaluation.

Comparison of accuracy for detecting coronary artery disease and side-effect profile of dipyridamole thallium-201 myocardial perfusion imaging in women versus men.

Intravenous dipyridamole planar thallium-201 imaging is a safe and effective test for detection and prognosis of coronary artery disease (CAD) in the general population. The relative diagnostic accuracy and side-effect profile of dipyridamole thallium-201 stress imaging in women is not defined. Forty-three consecutive female and 71 male patients who underwent dipyridamole thallium-201 imaging (0.56 mg/kg) within 3 months of cardiac catheterization were studied. Scans were considered abnormal if fixed or reversible perfusion defects were detected. Stenosis severity of greater than or equal to 50% luminal diameter reduction of any artery defined CAD. Overall sensitivity for detection of CAD was 0.87 in women and 0.94 in men; specificity was 0.58 in women and 0.63 in men (p = not significant). Sensitivity for detection of 1-vessel CAD was 0.60 in women and 0.94 in men (p = 0.001). The sensitivity for detection of multivessel CAD (with or without surgical revascularization) was 1.0 and 0.94 in women and men, respectively. Adverse effects were reported in 62% of women and in 38% of men (p = 0.01). There was no significant difference in the incidences of chest pain, headache, nausea, flushing or electrocardiographic changes. The incidences of severe ischemia and dizziness were higher in women. Possible explanations for this difference in adverse effects include gender differences in the volume of distribution of dipyridamole due to varied fat-to-muscle ratios and different subjective nocioceptive sensitivities to the effects of dipyridamole. Overall sensitivity and specificity are comparable between the sexes.

Prognostic value of dipyridamole thallium-201 imaging in elderly patients.

The prognostic value of intravenous dipyridamole myocardial perfusion imaging has not been studied in a large series of elderly patients. Patients greater than or equal to 70 years of age with known or suspected coronary artery disease were evaluated to determine the predictive value of intravenous dipyridamole thallium-201 imaging for subsequent cardiac death or nonfatal myocardial infarction. Of the 348 patients, 207 were symptomatic and 141 were asymptomatic; 52% of the asymptomatic group had documented coronary artery disease. During 23 +/- 15 months of follow-up, there were 52 cardiac deaths, 24 nonfatal myocardial infarctions and 42 revascularization procedures (percutaneous transluminal coronary angioplasty in 20; coronary artery bypass surgery in 22). Clinical univariate predictors of a cardiac event included previous myocardial infarction, congestive heart failure symptoms, hypercholesterolemia and diabetes (all p less than 0.05). The presence of a fixed, reversible or combined thallium-201 defect was significantly associated with the occurrence of cardiac death or myocardial infarction during follow-up (p less than 0.05). Cardiac death or nonfatal myocardial infarction occurred in only 7 (5%) of 150 patients with a normal dipyridamole thallium-201 study (p less than 0.001). Stepwise logistic regression analysis of clinical and radionuclide variables revealed that an abnormal (reversible or fixed) dipyridamole thallium-201 study was the single best predictor of cardiac events (relative risk 7.2, p less than 0.001). As has been demonstrated in younger patients, previous myocardial infarction (relative risk 1.8, p less than 0.001) and symptoms of congestive heart failure at presentation (relative risk 1.6, p = 0.02) were also significant independent clinical predictors of cardiac death or myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic value of exercise thallium scintigraphy in patients with good exercise tolerance and a normal or abnormal exercise electrocardiogram and suspected or confirmed coronary artery disease.

Exercise thallium scintigraphy is widely used to assess prognosis in patients with suspected or proven coronary artery disease. The incremental prognostic value of this technique in patients who have good exercise tolerance has not been well studied. Two hundred ninety-nine patients with known or suspected coronary artery disease without prior myocardial infarction or revascularization procedure referred for exercise myocardial perfusion imaging and able to exercise to greater than or equal to stage III of the Bruce protocol were included. After a mean follow-up of 50 +/- 10 months, there were 15 cardiac events (5%). The incidence of cardiac events was 10 versus 3% (p less than 0.001) in patients with an abnormal versus normal thallium-201 scan, and 9 versus 3% (p = 0.03) for an abnormal versus normal exercise electrocardiogram. When the 185 patients with a normal exercise electrocardiogram were examined, the incidence of cardiac events was 3% (5 of 150) in patients with a normal scan versus 0% (0 of 35) in patients with an abnormal scan. In the 114 patients with an abnormal exercise electrocardiogram, an abnormal thallium-201 scan was predictive of cardiac events (18% [8 of 44] versus 3% [2 of 70]; p = 0.006). Stepwise logistic regression analysis selected an abnormal thallium-201 scan and abnormal exercise electrocardiogram, low peak exercise heart rate, and male gender as independent variables associated with a significant increased risk of cardiac events. Thus, in patients with known or suspected coronary artery disease and good exercise tolerance, the addition of thallium-201 imaging in patients with an abnormal exercise electrocardiogram provides useful prognostic information.(ABSTRACT TRUNCATED AT 250 WORDS)