Biomedical subjects
G Bear
Publications and source records attributed to G Bear.
The functional significance of calcification of coronary arteries as detected on CT.
We evaluated the coronary arteries on computed tomography (CT) scans of the chest and on coronary angiograms of 27 patients who underwent both studies. We related the presence or absence of coronary artery calcification on CT to percentage stenosis on angiogram. For the left anterior descending artery (LAD), the likelihood of calcification rose proportionately with degree of stenosis; this was less true for the circumflex, and not true for the right coronary artery (RCA). The sensitivity of CT in detecting coronary artery calcification in patients with angiographic criteria of significant coronary artery disease (CAD) was 78% for the LAD, 63% for the circumflex, and 16% for the RCA. Specificities were 78%, 80%, and 100%, and positive predictive values were 88%, 83%, and 100%. The high positive predictive values suggest that coronary artery calcification diagnosed by chest CT has a high correlation with clinically significant CAD. Therefore, when we detect such calcification in a patient without documented heart disease, we suggest that a cardiac workup is indicated.
The hemodynamics of beta-blockade in patients undergoing abdominal aortic aneurysm repair.
To assess the intraoperative and postoperative hemodynamic effects of beta-blockade and its benefits in limiting myocardial ischemia and infarction, a group of 32 patients scheduled for abdominal aortic aneurysm (AAA) surgery (group 1) was treated with oral metoprolol immediately before surgery and with intravenous metoprolol during the postoperative period. Mean age was 71 years, and mean ejection fraction was 56% (range 36% to 83%). Eight patients had a preoperative history of angina, 13 had a history of myocardial infarction, and five had electrocardiographic evidence of prior myocardial infarction. A group of 51 closely matched patients with AAA who did not receive metoprolol served as controls (group 2). In group 1, overall hemodynamic tolerance of metoprolol intraoperatively and postoperatively was good, and there was no incidence of congestive heart failure, hypotension, or asthma. Furthermore, in group 1 significant reduction of systolic blood pressure and heart rate was consistently noted at frequent intraoperative intervals and for 48 hr after surgery, with only a transient reduction of cardiac index. In group 1, only one patient (3%) suffered an acute myocardial infarction. In contrast, nine group 2 patients (18%; p less than .05) suffered perioperative myocardial infarction. Furthermore, only four (12.5%) group 1 patients developed significant cardiac arrhythmias as opposed to 29 group 2 patients (56.9%; p less than .001). These data demonstrate that beta-blockade with metoprolol is effective in controlling systolic blood pressure and heart rate both intraoperatively and postoperatively in patients undergoing repair of AAA and can significantly reduce the incidence of perioperative myocardial infarction and arrhythmias.
The value of the radionuclide angiogram in the prediction of perioperative myocardial infarction in patients undergoing lower extremity revascularization procedures.
To better define the group of patients at high risk of myocardial infarction (MI) and death associated with lower extremity revascularization procedures, resting gated blood pool studies were obtained in 100 such patients before surgery and results were correlated with the prevalence of perioperative MI. The results indicated that three patient groups could be distinguished on the basis of cardiac ejection fraction. Group I (n = 50) had preoperative ejection fractions ranging from 56% to 83%. None of the patients in group I suffered an acute perioperative MI. Group II (n = 42) comprised patients with ejection fractions ranging from 36% to 55%. There was a 19.0% prevalence of MI in group II, with one cardiac death. Group III included eight patients with ejection fractions ranging from 26% to 35%. There was a 75% prevalence of perioperative MI in these patients, with one cardiac death. All perioperative MIs occurred within the first 48 hr after surgery. Statistical analysis demonstrated a significantly higher prevalence of perioperative MI in patients with gated pool ejection fractions of 35% or less compared with the prevalence in patients with one or more of the other widely used clinical signs of increased cardiac operative risk (p less than .02).
The value of radionuclide angiography as a predictor of perioperative myocardial infarction in patients undergoing abdominal aortic aneurysm resection.
To define the group of patients at high risk for myocardial infarction (MI) and death associated with abdominal aortic aneurysm repair, resting gated blood pool studies were obtained on 50 such aneurysm patients preoperatively. The results indicated that three groups could be distinguished among these patients by cardiac ejection fraction. Group I (n = 25) had preoperative ejection fractions ranging from 56% to 85%. None of the patients in group I suffered an acute perioperative MI. Group II (n = 20) comprised patients with ejection fractions ranging from 36% to 55%. There was a 20% incidence of MI in group II but no cardiac deaths. Group III included five patients with ejection fractions ranging from 27% to 35%. There was an 80% incidence of perioperative MI in these patients, with one cardiac death and one cardiac arrest. All perioperative MIs occurred within the first 48 hours after surgery. In addition there was a 50% incidence of perioperative MI among all those patients who were 80 years of age or older. These results indicate guidelines for the management of patients undergoing abdominal aortic aneurysm repair based on their preoperative ejection fraction. The data further suggest that the noninvasive gated blood pool method of determining ejection fraction may serve a more broadly useful function in helping to determine which of those patients about to undergo major surgical procedures are at high risk for perioperative MI.
Long-term efficacy of bromocriptine in Parkinson disease.
Twenty-eight patients with Parkinson disease (PD) were treated with bromocriptine for at least 2 years (mean, 2.8 years; range, 2 to 5 years). All of them had first been treated with levodopa (alone or combined with carbidopa, as Sinemet) for 7.4 years (range, 1 to 10 years). At the time bromocriptine was started, all were showing increasing disability. In these patients, attempts to increase levodopa resulted in adverse effects, and attempts to decrease levodopa resulted in increased parkinsonism. Bromocriptine (mean daily dose, 56 mg) was added to levodopa and resulted in improvement of at least one stage (Hoehn and Yahr scale) in 21 of the patients. After 2 years, five of these patients continue to maintain this improvement. The remaining patients, although there has been deterioration, maintain some of their original improvement. Bromocriptine, when added to levodopa, results in improvement that is maintained, in part, for at least 2 years. The ratio of bromocriptine to levodopa has to be periodically readjusted.
Malfunctioning electrocardiographic monitor simulating sinus arrest.
A 64-year-old patient was admitted to the hospital with a history of two syncopal episodes. The results of the physical examination, resting electrocardiogram and His-bundle study were all normal. Study with a 24-hour ECG monitor (Holter) was at first interpreted as demonstrating periods of sinus arrest. However, more careful examination revealed that these actually represented transient speeding of the monitor tape, perhaps secondary to a semiconductor malfunction. Such monitor malfunction may stimulate severe rhythm disturbances.
Intracranial hemorrhage and infarction in anticoagulated patients with prosthetic heart valves.
In 1 year 6 patients with prosthetic heart valves (PHVs) treated with anticoagulants suffered intracranial hemorrhage. In 4, hemorrhage occurred into the site of a recent non-hemorrhagic infarction. In the others, both of whom had endocarditis, hemorrhages probably occurred as the result of rupture of a mycotic aneurysm. Five patients were treated with warfarin, 1 with heparin. In all patients the level of anticoagulant activity was greater than 1.5 times control. Five patients were in atrial fibrillation; 1 was hypertensive. The diagnosis of intracranial hemorrhage was made and its location and extent accurately determined by computed tomography (CT). Three patients underwent surgery and 2 are alive with only minor neurological deficits. Among the 3 patients who did not undergo surgery 2 died and 1 is alive with a moderate neurological deficit. The management of PHV patients with use of anticoagulants is discussed in terms of the mechanisms involved in intracranial bleeding. Emphasis is placed on prevention of emboli, discontinuation of anticoagulants once non-hemorrhagic infarction has occurred and the primacy of CT scan in diagnosis when hemorrhage is suspected. The special problems of anticoagulation in the presence of endocarditis are also discussed.