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Biomedical subjects

A J Roberts

Publications and source records attributed to A J Roberts.

At least 127 records · Page 7Linked to original sources
PubMed1983

Perioperative myocardial infarction and changes in left ventricular performance related to coronary artery bypass graft surgery.

Recent advances in perioperative management and surgical technique have been associated with low operative mortality and a high incidence of symptomatic relief in patients undergoing coronary artery bypass graft (CABG) operations. The frequency and importance of perioperative myocardial infarction (MI) and immediate as well as long-term changes in left ventricular (LV) performance are factors of considerable current interest in any critical analysis of the effectiveness of CABG surgery. The present review describes the effects of patient selection, anesthetic techniques, and newer methods of myocardial protection as they relate to perioperative MI and LV performance. In addition, newer tests useful in the diagnosis of perioperative MI are discussed. The application of noninvasive techniques for the serial determination of LV performance and myocardial perfusion in CABG operations is also described.

Anesthesia↗
PubMed1983

Comparison of early and long-term results with intraoperative transluminal balloon catheter dilatation and coronary artery bypass grafting.

Twenty-six patients with chronic stable angina underwent intraoperative coronary artery balloon catheter dilatation and concomitant coronary artery bypass grafting (CABG). In one patient (3.8%) the catheter could not be passed through the arterial narrowing, and in two patients (8%) early angiographic evidence for arterial damage was detected. Postoperative angiographic data were available in 85% of patients early (mean 10 days) and in 50% of patients late (mean 12 months). Early results showed one perioperative myocardial infarction, 100% relief of angina, and no operative mortality. Compared to preoperative studies, of 23 angiographically visualized distal narrowings dilated in an antegrade fashion, 12 (52%) were unchanged, two (9%) were worse, and nine (39%) were improved. Those arterial segments with discrete distal narrowings (n = 13) had better angiographic results than those with diffuse distal narrowings (n = 9). In 49% of the former and in 22% of the latter arterial narrowings, improvement (increased luminal diameter) was documented postoperatively. In addition, there were four proximal narrowings which were dilated in a retrograde fashion; three were unchanged and one was improved compared to preoperative studies. Only one of 27 dilated segments (3%) was totally occluded postoperatively. Late results showed two patients (8%) developed recurrent chest pain and one patient (4%) died related to congestive heart failure. The two patients who had angiographically documented coronary arterial intimal injury showed evidence of resolution at late study. In 13 distal narrowings, six (46%) were unchanged, three (23%) were worse, and four (31%) were improved compared to the preoperative appearance. In 10 distal narrowings visualized both early and late postoperatively, nine were unchanged and one was worse. In summary, coronary artery balloon catheter dilatation during CABG is relatively safe and is associated with acceptable clinical results. Angiographic evidence for improvement is less than symptomatic relief postoperatively. Therefore, objective evaluation may be necessary for accurate determination of operative results. The need for a national registry related to intraoperative angioplasty is probably warranted.

Angina Pectoris↗
PubMed1983

The efficacy of medical stabilization prior to myocardial revascularization in early refractory postinfarction angina.

The timing of coronary artery bypass graft (CABG) surgery in patients with persistent, severe myocardial ischemia after an acute myocardial infarction is controversial. Based on the previous disappointing clinical experience with urgent surgery, a period of medical stabilization (mean ten days, range two to 28) prior to surgery was employed in a prospective nonrandomized clinical trial. The frequent use of intravenous nitroglycerin and intra-aortic balloon pumping was important in allowing preoperative clinical stabilization in these patients who were refractory to conventional medical therapy. The combined medical-surgical treatment protocol was associated with no early or late mortality in 20 patients who suffered preoperative myocardial infarction and demonstrated refractory post-infarction angina. Although these patients were considered to be high-risk surgical candidates, the incidence of perioperative myocardial damage in this selected group was comparable with that observed in patients undergoing elective CABG surgery at this institution without recent preoperative myocardial infarction. In order to determine the hemodynamic effectiveness of this selected patient management process, perioperative changes in left ventricular performance were determined by multigated cardiac blood pool imaging. Computer-based analysis of this radionuclide-related data allowed the accurate determination of ejection fraction (EF). Those patients with preoperative subendocardial infarction (N = 12) had no decrease in global EF 24 hours after operation and significant increases in EF seven days and eight months after operation. This pattern is analogous to that observed in patients without preoperative myocardial necrosis undergoing elective CABG surgery at this institution. Those patients with recent preoperative transmural myocardial infarction (N = 8) showed a decrease in EF 24 hours after operation, but recovered to preoperative levels seven days and eight months after operation. There was, however, no increase in EF in this subgroup of patients. On the basis of this study, the authors tentatively recommend a concerted effort at preoperative medical stabilization prior to CABG surgery in patients with persistent refractory myocardial ischemia soon after acute myocardial necrosis. A prospective, randomized study comparing urgent and delayed surgery, as well as nonsurgical treatment, will be necessary to define more precisely optimal management of this subgroup of cardiac patients.

Angina Pectoris↗
PubMed1983

Cardiac and renal responses to cross-clamping of the descending thoracic aorta.

The present study was performed to document the relative efficacy of commonly applied techniques used adjunctively during 1 hour of descending thoracic aortic cross-clamping. Renal and cardiac responses were determined by standard laboratory methods. There were four experimental groups: (1) heparin-bonded shunt; (2) partial femoral-femoral bypass; (3) sodium nitroprusside; (4) control. Each of the experimental groups showed abnormal hemodynamic responses during cross-clamping. Elevations in left ventricular end-diastolic pressure (LVEDP) and systolic blood pressure were common events during clamping, and cardiac output often decreased. Nevertheless, left ventricular performance curves after cross-clamping showed similar increases in left ventricular stroke work (LVSW) with increasing preload. In addition, left ventricular biopsy specimens showed preservation of myocardial high-energy phosphate stores and essentially normal ultrastructural integrity. Radioactive microspheres generally showed increased myocardial blood flow during and after cross-clamping, but no evidence of preferential subendocardial ischemia. Examination of renal function showed a marked decrease in urine output, glomerular filtration rate, and renal plasma flow during cross-clamping. Following the release of the cross-clamp, renal function returned to 50% to 85% of baseline status. Since we could find no major advantage of any of the techniques employed under the present experimental conditions, we suggest that all of the techniques should be part of the surgical armamentarium and the particular preoperative and/or intraoperative findings in a specific case should determine which technique is most appropriate for a given patient.

Adenosine Triphosphate↗
PubMed1982

Clinical evaluation of the relative effectiveness of multidose crystalloid and cold blood potassium cardioplegia in coronary artery bypass graft surgery: a nonrandomized matched-pair analysis.

Controversy exists concerning the most effective method of myocardial protection during coronary artery bypass graft operations. Accordingly, we performed a matched-pair analysis between 25 patients receiving multidose hypothermic potassium crystalloid cardioplegia and 25 other patients receiving cold blood potassium cardioplegia. Patients were matched on the basis of preoperative ejection fraction (EF) and the number of anatomically similar stenotic coronary arteries. The adequacy of myocardial protection was assessed by serial perioperative determinations of radionuclide ventriculography, hemodynamic measurements, analyses of electrocardiograms and serum levels of MB-CK. We found that the level of myocardial protection was similar between unstratified groups. However, when subgroups were selected on the basis of prolonged aortic cross-clamp time (greater than ninety minutes) or impaired preoperative left ventricular function (EF less than 40%), there was a suggestion that cold blood cardioplegia may be advantageous.

Adult↗
PubMed1982

Preliminary experience with intraoperative transluminal balloon-catheter dilation and coronary artery bypass grafting for the treatment of symptomatic diffuse coronary artery disease.

Transluminal balloon-catheter dilation of coronary artery lesions has become increasingly common in the cardiac catheterization laboratory. We describe a method of intraoperative dilation that may improve surgical results when used in combination with coronary artery bypass graft (CABG) operations in patients with diffusely diseased coronary arteries. In 16 patients, long-segment intraoperative dilations were performed to enlarge luminal narrowings in 21 different regions. All of these patients had postoperative coronary angiography and left ventriculography so that we could objectively evaluate the coronary dilatations. There were no operative deaths or perioperative myocardial infarctions, and angina was relieved in all patients. Of the 21 dilated segments, 12 (57%) were unchanged, 2 (10%) became worse, and 7 (33%) were improved postoperatively. In addition, two new areas of intimal damage were detected in patients with unchanged postoperative liminal diameters. We conclude that further experience and longer follow-up are necessary before the efficacy of intraoperative coronary artery balloon-catheter dilation can be accurately determined.

Angioplasty, Balloon↗
PubMed1981

Nonrandomized matched pair analysis of intermittent ischemic arrest versus potassium crystalloid cardioplegia during myocardial revascularization.

The quest for the ideal method of myocardial preservation during coronary artery bypass graft (CABG) surgery continues at a rapid pace. Nevertheless, in the present clinical practice of cardiac surgery, the choice is chiefly between hypothermic intermittent ischemic arrest and hypothermic potassium cardioplegia. This study applies newer technics in radionuclear cardiology, as well as more conventional enzymatic, electrocardiographic, and hemodynamic determinations, to the evaluation of the effectiveness of the previously mentioned modes of myocardial protection. Serial assessments are made preoperatively as well as during the first ten days postoperatively. We find that the perioperative incidence of myocardial damage and changes in left ventricular performance are almost identical using either method in patients with relatively normal preoperative left ventricular performance who do not have severe preoperative refractory ischemia or necrosis.

Aged↗
PubMed1981

Accuracy in coronary graft flow measurement.

A blood flow calibration apparatus is described for use with electromagnetic flow probes. It is an automatic gravity-flow system, which provides a constant level and therefore constant flow at any preset rate. On several occasions, the use of this device has helped to determine whether flow probes require simple adjustment, factory repair, or replacement. Using this system, a systematic error in the manufacturer's "precalibration" averaging +22% (range, 9 to 50%) has been discovered, and appropriate corrections have been made. The accuracy of these corrections has been confirmed by a rapid, in vivo method of calibration, which also is described and which can be carried out during the conduct of aortocoronary bypass operation. It is recommended that all groups measuring coronary graft flow become familiar with their electromagnetic flowmeter and probes by means such as those described, in the interest of accurate flow measurement after bypass operation.

Blood Flow Velocity↗
PubMed1981

Serial assessment of left ventricular performance following coronary artery bypass grafting. Early postoperative results with myocardial protection afforded by multidose hypothermic potassium crystalloid cardioplegia.

Forty patients who recently underwent coronary artery bypass graft (CABG) operations had serial hemodynamic and scintigraphic studies. Multidose hypothermic potassium crystalloid cardioplegia was used for myocardial protection and newer techniques in anesthetic management and perioperative patient care were also employed. The method of equilibrium cardiac gated blood pool (GBP) scintigraphy was used to obtain perioperative changes in global ejection fraction (EF) and regional wall motion (RWM). Ninety percent of patients displayed a decrease in EF 2 hours postoperatively when compared to their preoperative values. This change was also associated with a fall in cardiac index (CI) and left ventricular stroke work index (LVSWI). Twenty-four hours postoperatively, EF and CI recovered to preoperative levels, but LVSWI remained depressed. Seven days postoperatively, global EF had improved to a value greater than the preoperative one (50% +/- 3% versus 57% +/- 4%, p < 0.05). Perioperative changes in RWM followed the same pattern as EF, but recovery in this index of regional contractility was faster than EF, since maximal improvement was observed 24 hours postoperatively. Thus transient left ventricular dysfunction is common immediately after CABG, but recent advances in myocardial protection and perioperative management are associated with short-term increases in regional and global left ventricular function documented by noninvasive GBP imaging.

Aged↗
PubMed1980

Early and long-term improvement in left ventricular performance following coronary bypass surgery.

Changes in left ventricular performance after coronary artery bypass grafting (CABG) have been variable. Earlier studies based on contrast left ventriculography have shown occasional improvement in left ventricular function in patients with unstable angina or abnormal preoperative ventricular performance, but for the most part repeat cardiac catheterization several months after operation has shown no significant changes in global left ventricular contraction. In the past few years, advances in radiopharmaceutical technology have made the characterization of left ventricular wall motion accurate and highly reproducible. Since prognosis in patients with coronary artery disease and survival after CABG have been related to global ejection fraction (EF), we employed prospectively on analysis of short-term and long-term changes in EF after CABG utilizing multidose hypothermic potassium crystalloid cardioplegia as the method of myocardial protection. Concomitantly, newer techniques in anesthesia and perioperative patient management were employed to minimize myocardial damage in these patients. Postoperative scintigraphic evaluation showed a transient (2-hour) depression in left ventricular function, followed by recovery to preoperative levels at 24 hours and significant improvement in EF at 7 days. From 7 days to 8 months postoperatively, there was no further change in resting EF, but there was another significant exercise-induced increase in EF at the long-term examination. Thus, present advances in the multidisciplinary management of patients with coronary artery disease are associated with improvement in resting and exercise-related EF postoperatively.

Aged↗
PubMed1980

Advantages of hypothermic potassium cardioplegia and superiority of continuous versus intermittent aortic cross-clamping.

The relative effectivenss of hypothermic potassium (K) cardioplegia in conjunction with either continuous or intermittent aortic cross-clamping was evaluated in 20 mongrel dogs. Isovolumetric left ventricular (LV) contractions and myocardial biopsies were obtained before and after a total of 90 minutes of aortic cross-clamping. The dogs were randomly divided into four groups of five dogs each as follows: Group I, continuous 90 minute cross-clamping and multidose K at 4 degrees C (40 mEq/L); Group II, intermittent cross-clamping consisting of six 15 minute periods of cross-clamping separated by 5 minute reperfusion periods and K cardioplegia at 4 degrees C given at the start of each cross-clamping period; Group III, continuous 90 minute cross-clamping and multidose buffered saline at 4 degrees C; Group IV, intermittent cross-clamping, consisting of six 15 minute periods of cross-clamping separated by 5 minute reperfusion periods and buffered saline at 4 degrees C given at the initiation of each cross-clamp period. Group I dogs had the best myocardial performance, with no difference between control values of peak LV pressure and dP/dtmax and those recordings obtained 60 minutes after release of the aortic cross-clamp. Significant depression of LV function was noted in all other groups. Examination of force-velocity and length-tension relationships confirmed better myocardial performance in Groups I and II (multidose K at 4 degrees C) than in Groups III and IV (buffered saline at 4 degrees C). Groups I and III (continuous cross-clamping) had no de-rease in diastolic LV compliance after cross-clamping, whereas compliance was decreased in both Groups II and IV (intermittent cross-clamping) at higher preloads (p less than 0.05 and p less than 0.025, respectively). The wet weight/dry weight myocardial ratios were lower in Groups I and III (continuous cross-clamping) than in Groups II and IV (intermittent cross-clamping). Although creatine phosphate (CP) concentrations were rapidly restored by reperfusion in all groups, adenosine triphosphate (ATP) and glycogen myocardial stores were better preserved at the end of cross-clamping in Groups I and II (multidose K at 4 degrees C). Although LV diastolic compliance was decreased and myocardial water content was increased in Groups II and IV (intermittent cross-clamping), no differences in the minimal extent of subendocardial hemorrhage, edema, and contraction-band necrosis were observed among any of the groups examined electron microscopically. The present study identifies continuous aortic cross-clamping with multidose K at 4 degrees C as a superior method of myocardial protection.

Animals↗
PubMed1979

Thoracic aortic imaging without angiography.

Imaging of the thoracic aorta without recourse to angiography has great theoretic appeal. We have used computerized tomography (CT) in the initial evaluation of 297 patients with suspected mediastinal disease. Nineteen of this group had important findings related to the thoracic aorta: aortic dissection (six), descending thoracic aortic aneurysm (nine), suspected aortic trauma (three), and suspected false aneurysm at a coarctation repair (one). In all cases, the aorta and related pathology were readily demonstrated by CT, aided by the intravenous infusion of contrast material. In 13 of 15 cases, aortic dissection and aortic aneurysm could be accurately diagnosed. In two instances of ascending aortic dissection, it was not possible to distinguish the false lumen from mural thrombus in an atherosclerotic aneurysm.

Aorta, Thoracic↗
PubMed1979

Effects of the converting enzyme inhibitor (SQ 20881) on the pulmonary circulation in man.

The effects of the converting enzyme inhibitor (SQ 20881) on the pulmonary circulation were investigated in 13 patients in whom systemic hypertension developed following coronary artery bypass surgery. Pulmonary vascular resistance was decreased by the inhibitor, from 128 +/¿ 19 to 92 +/- 20 dynes sec cm-5 (or by 30 +/- 7 per cent; P less than 0.005), and this resulted in a decrease in mean pulmonary artery pressure from 17 +/- 1 to 13 +/- 1 mm Hg (or by 23 +/- 3 per cent, P less than 0.005). Consequently, right ventricular work was decreased by the inhibitor by 30 per cent (P less than 0.01), despite an increase in cardiac output (increase in stroke volume) by 16 +/- 6 per cent (P less than 01). This increase occurred despite a 13 +/- 3 per cent decrease in right ventricular filling pressure. The changes in pulmonary vascular resistance correlated with the pretreatment plasma renin activity (r = 0.74, P less than 0.01), as did the decrease in mean pulmonary artery pressure (R = 0.82, P less than 0.001), but neither change was related to the decrease in left ventricular fillling pressure nor to changes in cardiac output or mean arterial pressure. These results indicate that blockade of the formation of angiotensin II by the converting enzyme inhibitor results in reductions in pulmonary vascular resistance and pulmonary artery pressure which are unrelated to alterations in left ventricular function. Thus, angiotensin inhibition may have therapeutic value in various clinical states characterized by pulmonary hypertension--especially if renin levels are high.

Adult↗