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Biomedical subjects

H S Loeb

Publications and source records attributed to H S Loeb.

At least 37 records · Page 2Linked to original sources
PubMed1990

Effects of ionic and nonionic contrast media on bradyarrhythmia during coronary angiography: a comparison of Renografin-76, Hypaque-76, and Isovue-370.

Contrast media occasionally produce bradyarrhythmias defined as a 25% decrease in heart rate and/or developing atrioventricular block during coronary angiography. Twelve left coronary angiographies and seven right coronary angiographies were performed with 10 ml of diatrizoate meglumine and diatrizoate sodium (Renografin-76 [R76] or Hypaque [H76]) or iopamidol (Isovue 370 [ISO]) in a blinded randomized fashion. Heart rate decreased significantly from 135 +/- 5 to 120 +/- 5 beats/min (p less than 0.001) with R76, to 127 +/- 7 beats/min (p less than 0.01) with H76, and to 130 +/- 6 beats/min (p less than 0.05) with ISO in left coronary angiographies; more profound decrease was observed in right coronary angiographies from 134 +/- 4 to 87 +/- 18 beats/min (p less than 0.001) with R76, to 99 +/- 14 beats/min (p less than 0.001) with H76, and to 125 +/- 7 beats/min (p less than 0.01) with ISO. In 12 left coronary angiographies bradyarrhythmia was observed in five cases with R76, two with H76, and none with ISO. In seven right coronary angiographies it occurred in six with R76, three with H76, and none with ISO. The differences in the incidence of bradyarrhythmia between R76 and ISO were significant during left and right coronary angiographies (p less than 0.05 and p less than 0.01, respectively). Thus ionic contrast media produced more marked bradyarrhythmias than nonionic contrast media in coronary angiography, especially R76. Right coronary angiography resulted in more profound bradyarrhythmias than left coronary angiographies. This study suggested that nonionic contrast media (ISO) might be preferable to ionic contrast media (R76 or H76) for coronary arteriography.

Angiography↗
PubMed1989

The potential risk of thrombosis during coronary angiography using nonionic contrast media.

The influence of contrast media on coagulation has an important association with thromboembolic complication during coronary angiography. In this study, whole blood was methodically mixed with nonionic contrast medium, Iohexol (IOH), conventional ionic contrast medium, Hypaque-76 (H76), and low osmolar ionic dimer Hexabrix (HB) in vitro. The thrombotic propensity of contrast agents can be evaluated by measuring the clot formation of the mixtures. The experiments were repeated with whole blood after systemic heparinization. In the in vitro study, 5 ml of canine (N = 10) and 3 ml of human (N = 11) whole blood was incubated for 30 min in glass tubes with equal volumes of IOH, H76, HB, and 0.9% NaCl before heparinization. Clot formation with IOH and 0.9% NaCl were seen both in dogs (4.0 +/- 0.7 gm and 5.6 +/- 0.8 gm) and in patients (1.4 +/- 0.9 gm and 2.9 +/- 1.3 gm), whereas no clot was seen with H76 or XB. Following heparinization, no clot was visualized in any mixture of whole blood with contrast media or 0.9% NaCl. Similar results were observed in the catheter-syringe system with canine blood (N = 11) mixed with the contrast agents. Blood clots found in 15 min and 30 min of IOH were 0.07 +/- 0.08 gm and 0.44 +/- 0.20 gm (P less than 0.01) and of NaCl were 0.29 +/- 0.37 gm and 0.69 +/- 0.38 gm (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1989

The mechanism and significance of ventricularization of intracoronary pressure during coronary angiography.

Ventricularization of pressure during coronary angiography has been said to identify the presence of left main coronary artery disease, but the hemodynamic features and the mechanism of this process have not been studied. Twenty consecutive patients with ventricularization were identified prospectively in our laboratory. Four patients had a discrete ostial left main stenosis and 16 patients had stenosis of the entire length of the left main coronary artery. The degree of pressure drop upon cannulation of the diseased left main coronary artery was highly variable; the systolic pressure decreased by 9 to 94 mm Hg, and the diastolic pressure decreased by 6 to 60 mm Hg. The morphology of the ventricularized pressure was distinct. It had a presystolic deflection resembling an a wave. The upstroke of this waveform was slower and the downstroke was steeper than that of the aortic pressure. An identical waveform was observed in dogs after partial occlusion of the left main coronary artery with a balloon-tipped catheter. The waveform of the so-called ventricularized pressure is derived from the aortic pressure, which is altered by its transmission across the left main coronary stenosis. The appearance of ventricularization is an important clue to the presence of left main coronary artery disease.

Aged↗
PubMed1989

Constrictive pericarditis after cardiac surgery.

Forty-five patients were identified as having constrictive pericarditis after cardiac surgery. The mean patient age was 61 years (range, 40 to 77 years). Twenty-three of 37 patients with adequate clinical information were reported to have had a diagnosis of postpericardiotomy syndrome after the original surgery. The mean interval from original surgery to presentation with constriction was 23.4 months (range, 1 to 204 months). Computerized tomography was helpful in establishing a diagnosis of constriction in 23 of 29 patients (79%). Bypass graft patency was 93% (85 of 91 grafts). Severe pulmonary hypertension (pulmonary artery systolic pressure greater than or equal to 60 mm Hg) was present in nine patients; 8 had coexistent valvular disease (seven cases of mitral valve disease, and aortic valve disease in one). Thirty-seven of the 45 patients underwent pericardial stripping, 28 of whom experienced marked symptomatic improvement. One patient had persistent right heart failure, which was not documented to be secondary to constriction. Four patients had persistent constrictive physiologic conditions. Three of these patients had more extensive pericardial stripping and showed clinical improvement. Four patients (11%) died within 30 days of stripping. Eight patients received medical therapy alone. The decision to treat patients medically was based either on favorable response to medical therapy (five patients), or poor general clinical status.

Coronary Artery Bypass↗
PubMed1988

Progression of coronary artery disease after percutaneous transluminal coronary angioplasty.

Thirty-nine patients underwent coronary arteriography 1 to 20 months (mean 7 months) after percutaneous transluminal coronary angioplasty (PTCA). At the time of the repeat study, 35 patients (90%) had recurrent angina or myocardial infarction, and 4 patients (10%) were asymptomatic. Restenosis, defined as greater than 50% loss of PTCA gained diameter, was found in 19 patients (49%). In addition, 20 patients had new lesions or marked progression of existing lesions (defined as greater than 20% or increasing greater than 20% obstruction in coronary diameter) in the previously normal or mildly diseased coronary segments. The new or progressive lesions occurred both in patients with restenosis at the PTCA site (nine of 19) and in patients without restenosis (11 of 20). New or progressive lesions tended to occur more commonly in the artery on which PTCA was performed (13 of 40) than in the artery that did not have PTCA (10 of 77) (p less than 0.02 by chi 2). In arteries that had PTCA, new or progressive lesions occurred more often in the segment proximal to the angioplasty site (seven of 13 or 54%) than in the peri-PTCA segment (two of 13 or 15%) and in the segments distal to it (four of 13 or 31%), but this observation did not reach statistical significance. No other clinical, angiographic, or PTCA procedure variables affected the occurrence of new or progressive lesions. In patients with recurrent angina or myocardial infarction after PTCA, both restenosis and new or progressive lesions are common. New lesions or marked progression of existing lesions tended to occur in the vessel subjected to PTCA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Effects of contrast media on the conducting system of the heart during coronary angiography. A comparison of Renografin-76 to Hypaque-76.

Electrocardiographic changes induced by ionic contrast media can cause complications during coronary angiography. A conduction delay through various parts of the heart is one factor in the genesis of asystole or ventricular fibrillation. Hypaque-76 (H76) and Renografin-76 (R76) are nearly identical ionic contrast media except that R76 binds more calcium than H76 because of the presence of sodium citrate and EDTA in R76. To determine whether the calcium binding additives in ionic contrast media contribute to the cardiac conduction abnormalities, we examined conduction time through the atrioventricular (AV) nodal tissue (via bipolar His bundle electrograms) and through the distal part of the conduction system (recording the QRS complex from the ECG) during coronary angiography. We injected 10 mL of H76 and R76 in 19 closed chest dogs in a blinded, randomized fashion during coronary angiography. The effects of H76 and R76 on heart rate, AH interval, HV interval, V interval and PR interval, and QRS complex duration were recorded. In 14 nonatrial pacing dogs, compared with H76, R76 produced a greater increase in the AV interval (32.9 +/- 6 milliseconds vs 12.4 +/- 2 milliseconds, P less than .01) and the PR interval (29.6 +/- 6 milliseconds vs 11.9 +/- 4 milliseconds, P less than .02). Additionally, the heart rate decreased 13.9 +/- 3.5 beats/minute from control with R76 compared with a decrease of 4.2 +/- 2.6 beats/minute from control with H76 (P less than .05). There was no significant difference between the prolongation of the HV interval and V interval, or QRS complex duration generated by R76 and H76.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1988

The effects of rapid volume expansion on the right and left cardiac filling pressures after coronary artery bypass surgery.

Rapid volume expansion is a diagnostic procedure which can reveal typical hemodynamics of pericardial constriction in patients with pericardial disease who have normal hemodynamics in their baseline state. We studied 20 patients with previous coronary artery bypass surgery in order to determine whether this operation results in some degree of pericardial constriction which could be demonstrated by rapid volume expansion. After infusing 1 L of physiologic saline solution over six minutes, the right atrial pressure increased by 5 +/- 2 mm Hg, the right ventricular diastolic pressure by 4 +/- 3 mm Hg, the pulmonary capillary wedge pressure by 7 +/- 3 mm Hg, and the left ventricular diastolic pressure by 7 +/- 4 mm Hg (mean +/- SD). Equalization of the left and right cardiac pressures was not observed, and the normal respiratory variation of the pressures was not altered by rapid volume expansion. Thus, the pericardial manipulation associated with the performance of coronary artery bypass surgery does not commonly result in the development of subclinical pericardial constriction.

Adult↗
PubMed1986

Effects of indomethacin on coronary hemodynamics, myocardial metabolism and anginal threshold in coronary artery disease.

The effects of orally administered indomethacin or placebo on coronary hemodynamics were studied in 23 patients with coronary artery disease. After indomethacin administration the systemic arterial pressure increased by 12 +/- 4% and the myocardial oxygen consumption by 24 +/- 11%. Coronary sinus flow did not change and coronary vascular resistance increased slightly. Oxygen saturation of the arterial blood did not change, but coronary sinus saturation decreased substantially. Hemodynamic values returned to normal 150 minutes after administration of indomethacin. During rapid atrial pacing, coronary sinus flow increased 79 +/- 14% above the rest value when pacing was done before indomethacin administration; only a 56 +/- 12% increase was seen when pacing was repeated after indomethacin. Peak heart rate achieved during atrial pacing, severity of angina and the degree of ST-segment depression were not altered by indomethacin treatment. Orally administered indomethacin has a mild coronary vasoconstrictive effect that does not interfere substantially with the expected increase in myocardial blood flow during rapid atrial pacing. Anginal threshold is not altered by orally administered indomethacin.

Administration, Oral↗
PubMed1986

Effect of acute postinfusion lipemia and free fatty acids on myocardial contractility: assessment with radionuclide ventriculography.

Equilibrium gated radionuclide ventriculography was used to evaluate the effect of intravenous fat-emulsion overload and excess of free fatty acids (FFA) on left ventricular ejection fraction (LVEF) in 20 patients with and without coronary artery disease (CAD). Fifteen of these patients had normal (greater than 50%) baseline LVEF and 5 had low (less than 50%) baseline LVEF. From 100 to 150 ml of 20% artificial fat emulsion (Liposyn) was infused over 20-25 min. At the end of the infusion, triglyceridemia reached 820 +/- 220 mg% and left ventricular ejection fraction decreased from baseline 62 +/- 19% (mean +/- SD) to 58 +/- 16% (P less than 0.05, paired t-test). After completion of Liposyn infusion, 5,000 U of heparin was administered intravenously and monitoring of LVEF was continued. One and one-half hours following heparin administration, plasma FFA levels reached 3.7 + 2.0 mmol/l and LVEF rose to 69 +/- 19% (P less than 0.001, paired t-test). Our data indicate that acute intravenous fat overload can suppress and high pathophysiologic levels of FFA can increase LVEF. This effect is more uniform and statistically more reliable in patients with normal LVEF. The study failed to demonstrate any significant difference in the effect of this pharmacologic intervention between patients with and without CAD.

Aged↗
PubMed1986

The usefulness of dobutamine in the assessment of the severity of mitral stenosis.

Patients with mitral stenosis often require supine exercise in order to increase their heart rate and cardiac output to assess the severity of their valvular obstruction during cardiac catheterization. We substituted dobutamine for exercise in 14 patients with suspected mitral stenosis. The dobutamine infusion was started at 5 micrograms/kg/min and was increased to 10, 15, and 20 micrograms/kg/min every 3 minutes as tolerated. The heart rate increased from 84 +/- 4 to 123 +/- 7 bpm (p less than 0.001), the cardiac index increased from 2.4 +/- 0.2 to 3.4 +/- 0.2 L/min/m2 (p less than 0.001), and the mean pulmonary artery pressure increased from 27 +/- 3 to 30 +/- 2 mm Hg (p less than 0.02). The pulmonary wedge pressure of 19 +/- 2 mm Hg and the mitral valve index of 0.8 +/- 0.1 cm2/m2 remained unchanged, but the left ventricular end-diastolic pressure decreased from 11 +/- 2 to 6 +/- 2 mm Hg (p less than 0.02). The hemodynamic response during the infusion of dobutamine identified a subgroup of patients with more severe mitral stenosis. Thus, the administration of dobutamine is useful in the evaluation of the severity of mitral valve obstruction during catheterization.

Adult↗
PubMed1986

The response of patients with complex ventricular arrhythmias secondary to dilated cardiomyopathy to programmed electrical stimulation.

A prospective study was undertaken to assess the response of patients with idiopathic dilated cardiomyopathy to programmed electrical stimulation (PES). Fifteen patients undergoing evaluation of congestive heart failure were studied. All patients underwent cardiac catheterization and coronary angiography as well as endomyocardial biopsy to exclude known causes of heart failure. No patient had a history of syncope or sustained ventricular arrhythmias. All patients were found to have severe left ventricular dysfunction (mean ejection fraction 17%), as well as nonsustained ventricular tachycardia on ambulatory monitoring or exercise testing. A protocol using up to two premature stimuli and burst pacing, from two right ventricular sites, induced up to four repetitive ventricular responses but failed to induce a sustained ventricular arrhythmia in any patient. Patients with dilated cardiomyopathy, advanced ventricular arrhythmias, and depressed left ventricular function respond differently than do patients with coronary artery disease, advanced ventricular arrhythmias, and depressed left ventricular function, to PES. PES appears to have limited value in the evaluation of patients with dilated cardiomyopathy and nonsustained ventricular arrhythmias.

Adult↗
PubMed1986

Augmentation of cardiac output by external cardiac pacing: pacemaker-induced CPR.

Transthoracic cardiac pacing is frequently associated with simultaneous stimulation of skeletal muscle and nerves. We describe a patient in cardiogenic shock and complete heart block in whom the associated vigorous abdominal and chest muscle contractions caused by transthoracic cardiac pacing resulted in a marked augmentation of cardiac output and systemic blood pressure via a "CPR" effect.

Aged↗
PubMed1986

Pacemaker malfunction: fact or artifact?

In summary, the present examples illustrate how pacemaker malfunction can be simulated by the sources of artifact produced or detected by the monitoring equipment. This form of pseudopacemaker malfunction remains a common cause of mistaken diagnosis of pacemaker malfunction. A thorough understanding of the examples outlined above should help distinguish true pacemaker malfunction from pseudopacemaker malfunction produced by artifact.

Amplifiers, Electronic↗
PubMed1985

Ventricular fibrillation during coronary angiography: reduced incidence in man with contrast media lacking calcium binding additives.

The intracoronary injection of contrast media during coronary angiography occasionally results in ventricular fibrillation. Experimental studies have implicated the calcium sequestering agents, sodium citrate and EDTA in Renografin 76 (RG76), as contributing to this complication. Angiovist 370 (AV370) is a contrast medium similar to RG76 except that it contains disodium calcium EDTA instead of EDTA and sodium citrate. To determine if contrast media lacking sodium citrate and EDTA will result in a lower incidence of ventricular fibrillation in man, this investigation compared the incidence of contrast media-induced ventricular fibrillation in patients undergoing coronary angiography with RG76 to that with AV370. Group A consisted of 2,500 consecutive patients undergoing coronary angiography with RG76 and group B consisted of 2,000 subsequent consecutive patients in whom AV370 was employed as the contrast medium. There was no significant difference between groups A and B with respect to the volume of contrast media used per patient (153 +/- 49 ml vs 154 +/- 45ml), age (58.4 +/- 10 vs 58.6 +/- 10 years), sex (70% male vs 70% male), ejection fraction (59 +/- 17 vs 60 +/- 20), history of mitral valve disease (5.8% vs 7.1%), history of aortic valve disease (6.7% vs 6.5%), prior coronary artery bypass graft surgery (6.6% vs 7.3%), or extent of coronary artery disease. Fifteen episodes of contrast media-induced ventricular fibrillation occurred in group A (incidence 0.6%) whereas two episodes occurred in group B (incidence 0.1%) (p less than 0.02). Each patient was successfully defibrillated and no adverse sequelae resulted. Thus the present investigation suggests that the incidence of ventricular fibrillation during coronary angiography can be significantly decreased by using contrast media lacking sodium citrate and EDTA.

Aged↗
PubMed1985

Acute anterior myocardial infarction complicated by mural thrombus and peripheral thromboembolism despite anticoagulation.

A 43-year-old man had transmural anterior wall myocardial infarction complicated by hypotension and anterior-apical aneurysmal formation. Despite continuous anticoagulation with heparin sodium (heparin) and warfarin sodium (coumadin), a large pedunculated left ventricular thrombus was formed. Four hours after uneventful left ventriculography, the patient experienced acute superior mesenteric embolism. An emergency mesenteric embolectomy and then left ventricular aneurysmectomy with clot evacuation were performed to save the bowel and to prevent further embolization.

Adult↗
PubMed1985

The effects of acute hypertriglyceridemia and high levels of free fatty acids on left ventricular function.

The effects of acute hypertriglyceridemia and of high levels of free fatty acids on the left ventricular ejection fraction were studied by radionuclide ventriculography in 20 subjects with and without coronary artery disease. An infusion of approximately 125 ml of a 20% fat emulsion over 25 minutes resulted in an increase of plasma triglycerides to the mean of 820 mg/dl and a fall of the left ventricular ejection fraction from the baseline mean of 62% to 58% (p less than 0.05). Ninety minutes after the intravenous administration of 5000 units of heparin, plasma free fatty acids rose to the mean of 4.6 mmol/L and the mean left ventricular ejection fraction increased to 69% (p less than 0.001). The observed changes in blood lipids were not associated with clinical or ECG evidence of myocardial ischemia. We conclude that acute hypertriglyceridemia causes slight depression of left ventricular performance, while high levels of free fatty acids augment it. However, neither hypertriglyceridemia per se nor its rapid conversion to free fatty acids are likely to cause angina in stable patients with coronary artery disease.

Aged↗