Search PubMed⌕ Search

Biomedical subjects

S Khuri

Publications and source records attributed to S Khuri.

At least 37 records · Page 2Linked to original sources
PubMed1988

Operative mortality in patients undergoing single valve replacement in teaching institutions--early mortality as a function of resident versus staff surgeon.

Nine hundred sixty-four patients undergoing single valve replacement (SVR) procedures alone or in combination with other cardiac surgical procedures were analyzed prospectively to determine whether the risks of operative mortality (OM) are different when the operation is performed by a resident under direct supervision of an attending surgeon (group I, 49.5%) or by an attending surgeon (group II, 50.5%). The overall OM rate was 8.4% (7.2% for group I and 9.7% for group II, which was not significant). Fifty-eight clinical, angiographic, and hemodynamic variables were analyzed to adjust statistically for differences in patient characteristics in each group. For aortic valve replacement, group II patients had smaller valve area and a higher incidence of three-vessel coronary artery disease, and more patients required resection of an ascending aortic aneurysm, whereas group I patients had higher incidence of peripheral edema and S3 gallop. For mitral valve replacement, more patients in group II had pleural effusion, previous cardiac operations, higher mean pulmonary artery pressures, mitral insufficiency due to coronary artery disease, and were in New York Heart Association (NYHA) functional class 3 and 4, whereas the group I patients had higher incidence of S3 gallop and elevated serum creatinine. Expected OM for each group was derived from a multivariate logistic model. Ratio of observed-to-expected (O/E) OM was calculated to adjust observed OM according to the risk of patients. There was no difference in O/E mortality ratio between the two groups. We conclude that OM probability is not increased when the SVR procedure is performed by residents under direct supervision of attending surgeons when adjusted for patient- and disease-related risk factors. These findings also constitute compelling evidence that patient care does not suffer when resident teaching experience is enhanced in teaching institutions.

Aortic Valve↗
PubMed1987

Comparison of outcome after valve replacement with a bioprosthesis versus a mechanical prosthesis: initial 5 year results of a randomized trial.

The Veterans Administration Cooperative Study on Valvular Heart Disease was organized to compare survival and incidence of valve-related complications between patients receiving a bioprosthesis (the Hancock porcine heterograft) and a mechanical prosthesis (the Björk-Shiley spherical disc valve). Five hundred seventy-five patients undergoing single aortic or mitral valve replacement were randomized at surgery to one of the two valve types. At an average follow-up of 5 years (range 3 to 8) there are no statistically significant differences in survival between patients with the two valve types in the aortic valve replacement group. There is a statistically nonsignificant trend toward improved survival in patients undergoing mitral valve replacement with a bioprosthesis compared with a mechanical prosthesis (5 year survival probability was 0.70 +/- 0.05 and 0.58 +/- 0.06, respectively). Fatal and nonfatal valve-related complications occurred significantly less frequently in patients with a bioprosthesis compared with a mechanical prosthesis for both mitral and aortic valve replacement. Five year complication-free probability was 0.67 +/- 0.05 and 0.45 +/- 0.06, respectively, for patients with mitral valve replacement and 0.63 +/- 0.04 and 0.53 +/- 0.04, respectively, for those with aortic valve replacement. The difference in overall complication rates was largely due to the increased number of clinically significant but nonfatal bleeding episodes in patients receiving a mechanical prosthesis. Adjustment for differences in baseline characteristics between patients receiving a mitral mechanical prosthesis and a mitral bioprosthesis reduced the statistical significance of the difference in both mortality and complications.

Aortic Valve↗
PubMed1987

Hypothermia-induced reversible platelet dysfunction.

Baboons that were subjected to systemic hypothermia at 32 C had an arm skin temperature of 27.3 C and bleeding time of 5.8 minutes. With local warming of the arm skin to 34 C, the bleeding time was 2.4 minutes. In normothermic baboons with arm skin temperature of 34.6 C, the bleeding time was 3.1 minutes. Local cooling of the arm skin to 27.6 C produced a bleeding time of 6.9 minutes. Increasing the skin temperature of the arm in hypothermic baboons to 38.9 C and in normothermic baboons to 40.1 C reduced bleeding times to 2.1 and 2.3 minutes, respectively. In both hypothermic and normothermic baboons there was a negative and significant correlation between the bleeding time and the arm skin temperature and the thromboxane B2 level in the shed blood obtained at the template bleeding time site. There was a significant positive correlation between the thromboxane B2 level in the shed blood and the arm skin temperature. Both in-vivo and in-vitro studies have shown that the production of thromboxane B2 by platelets is temperature-dependent, and that a cooling of skin temperature produces a reversible platelet dysfunction. Data also suggest that when a hypothermic patient bleeds without surgical cause, skin and wound temperature should be restored to normal before the administration of blood products that are not only expensive but may also transmit disease.

Animals↗
PubMed1987

Clinical, hemodynamic, and angiographic predictors of operative mortality in patients undergoing single valve replacement. Veterans Administration Cooperative Study on Valvular Heart Disease.

Preoperative characteristics of 964 patients in the Veterans Administration Cooperative Study on Valvular Heart Disease undergoing single valve replacement were examined to determine predictors of operative mortality. The operative mortality rate was 8.3% in 661 patients having isolated aortic valve disease and 7.5% in 239 patients having isolated mitral valve disease, but 12.5% in 64 patients with multivalve disease undergoing single valve replacement. For the aortic valve replacement subgroup, three-vessel coronary artery disease, left ventricular systolic pressure, prior cardiac operation, body surface area, and cardiac index were related to operative mortality. In the mitral valve replacement group, there was a strong association of operative mortality with advanced age, exertional dizziness, reduced cardiac index, left ventricular contraction grade, ST segment depression on the resting electrocardiogram, and pleural effusion. The risk of operative death for an individual patient undergoing aortic or mitral valve replacement may be estimated with the use of independent risk factors.

Adult↗
PubMed1984

Vulnerability to ventricular fibrillation in patients with clinically manifest ventricular tachycardia.

Ventricular vulnerability may be assessed by measuring the threshold current for the induction of ventricular fibrillation (VF). This technique has been widely utilized in animal experimentation and has been safely applied in a small number of clinical studies. We measured the VF threshold (VFT), using the single stimulus technique in 10 patients with coronary artery disease just prior to the institution of cardiopulmonary bypass. There were no adverse effects of VFT measurement. Three patients had nonsustained ventricular tachycardia (VT) on 24-hour ambulatory monitoring and had VFTs of 10, 14, and 16 mA. In this group VF was induced without any preceding repetitive ventricular responses. Seven patients had no repetitive forms on ambulatory monitoring. Their VFTs ranged from 30 to greater than 40 mA (mean greater than 37). Repetitive extrasystoles were regularly observed in this group at current intensities which ranged from 53% to 80% of the VFT. Thus patients with manifest VT appear to have an enhanced vulnerability to VF. Single or multiple responses were not observed in these patients but appeared to be present in patients with coronary disease and no demonstrable rhythm disorder.

Aged↗
PubMed1983

Quantitative detection of regional left ventricular contraction abnormalities by 2-dimensional echocardiography. Comparison of myocardial thickening and thinning and endocardial motion in a canine model.

Myocardial infarction (MI) was produced in 27 dogs by ligation of the left anterior descending coronary artery. Two-dimensional (2-D) echocardiograms were performed through the closed chest before and serially after coronary ligation, in both the acute and healing stages of MI. Two-dimensional echocardiographic studies performed before the animals were killed were analyzed for left ventricular (LV) contraction defects by 2 algorithms--1 involving systolic myocardial thickening and thinning and the other by determining the extent of endocardial motion to derive cavity area shrinkage. Using the thickening algorithm, myocardial dysfunction was detected in 93% of the animals with MI; with the area shrinkage method, contraction abnormalities were detected in 96% of the animals with MI. When the heart was divided from base to apex into 3 short-axis sections, the thickening algorithm showed a trend toward better identification of normal regions than the area shrinkage algorithm. However, in predicting the circumferential extent of MI, the thickening-thinning method of analysis showed no advantage over the endocardial motion method (r = 0.77, standard error of the estimate = 0.16 versus r = 0.76, standard error of the estimate [SEE] = 0.16; p = not significant [NS]). These observations support the concept that either algorithm can be used effectively to detect the presence and quantify the circumferential extent of MI.

Acute Disease↗
PubMed1983

Lack of effect of nitroglycerin on the transmural variation of tissue pH during fixed coronary stenosis.

A new MpH-measuring system was used to investigate the mechanism of action of intravenous NTG on pacing-induced myocardial ischemia during critical stenosis. In ten anesthetized open-chest dogs, two MpH electrodes were placed in a segment supplied by the CCA, one superficial and one deep. Atrial pacing at a rate 50 beats/min higher than baseline was instituted for a period of 10 min (Pacing I). Critical stenosis was then applied to the CCA. Three more similar periods of atrial pacing were instituted during critical stenosis. Pacing II was without any intervention, Pacing III was after the intravenous administration of a bolus of NTG, and Pacing IV was after the intravenous administration of NTG + A. NTG (metamarinol) during critical stenosis and atrial pacing did not alter preload and did not reduce afterload more than critical stenosis and atrial pacing alone. It did not significantly alter flow in the CCA measured by an electromagnetic flow meter. Consequently, the magnitude of fall in both endo- and epicardial MpH during critical stenosis and atrial pacing was no different with or without the administration of NTG. That under these conditions NTG failed to reduce the degree of myocardial ischemia suggests that the beneficial effects of NTG during fixed critical stenosis are determined primarily by its ability to reduce the determinants of myocardial oxygen demand, and not by a direct effect on the ischemic myocardium per se. The study also demonstrates for the first time a significant transmural gradient in MpH in the canine heart, even in the normal resting state.

Animals↗
PubMed1982

Serial evaluation of myocardial thickening and thinning in acute experimental infarction: identification and quantification using two-dimensional echocardiography.

Regional left ventricular function was studied serially by quantitative two-dimensional echocardiography (2-D echo) in 20 dogs after left anterior descending coronary artery ligation. Normal values for regional myocardial thickening were established in 20 healthy dogs and used as a standard to recognize abnormally contracting segments (ACS). In normal hearts, the mean percent thickening tended to increase from base (25.8%) to apex (34.0%), but showed considerable diversity from segment to segment (range 20.0-40.0%); nevertheless, at least some degree of thickening was seen in every segment. After coronary occlusion, myocardial segments either thinned or failed to thicken. At the papillary muscle level, there was an improvement in function between 2 and 48 hours, with thinning at 2 hours and thickening at 48 hours. Tissue infarct size (IS) determined at 48 hours was related to IS derived from a weighted summation of ACS at 2, 24 and 48 hours. At 2 hours, ACS considerably overpredicted and correlated poorly with tissue IS (25.3% vs 13.4%; r = 0.60); by 48 hours, IS predicted by ACS had decreased to 15.3% (p less than 0.05) and had an improved, but only fair correlation with tissue IS (r = 0.73, SEE = 4.9%). We conclude that there is considerable heterogeneity to myocardial thickening by 2-D-echo, but failure to thicken is not seen in the normal dog heart. In many dogs, the extent of myocardial dysfunction 2 hours after coronary ligation exceeds that seen later. Tissue IS is difficult to predict accurately from ACS. Since the amount of muscle dysfunction is not necessarily equivalent to the amount of tissue necrosis in acute myocardial infarction, ACS may be more appropriate used to tract the course of infarction rather than to predict IS.

Animals↗
PubMed1980

Echocardiographic features of an unruptured aneurysm of the right sinus of Valsalva.

A 2-cm aneurysm of the right sinus of Valsalva was documented in a patient with a prosthetic aortic valve. The M-mode findings differed from prior reports and mimicked those of aortic root dissection or a catheter placed in the right ventricular outflow tract. Two-dimensional echocardiograms readily distinguished the aneurysm of the right sinus of Valsalva from the alternative possibilities.

Adult↗
PubMedDate not supplied

[Differential diagnosis of osteomyelitis of the calcaneus].

The authers avalyse 6 cases of calcaneal osteomyelitis with rather chronic development. They present radiological and clinical differential diagnostic problems. Osteomyelitis was to seperate from Sever's disease, benign and malignant bone tumours. In 3 cases only histology or bacteriology allowed the proper diagnosis.

Adolescent↗