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Biomedical subjects

J J Morris

Publications and source records attributed to J J Morris.

At least 55 records · Page 3Linked to original sources
PubMed1986

Right ventricular sensitivity to metabolic injury during cardiopulmonary bypass.

To determine intrinsic right ventricular susceptibility to metabolic injury, we examined the effect of ischemia and reperfusion during cardiopulmonary bypass on right and left ventricular myocardial adenine nucleotide metabolism in the absence of ventricular work load as a determinant of energy production and utilization. Dogs were subjected either to 30 minutes of normothermic or hypothermic myocardial ischemia and reperfusion or to 60 minutes of potassium-arrested normothermic ischemia; serial ventricular biopsy specimens were assayed for adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, nucleoside, and base content. In each group the depletion rates of right and left ventricular nucleotides with ischemia did not differ. Mitochondrial ability to rephosphorylate the nucleotide pool during and after ischemia also did not differ in the two ventricles, and there were no detectable differences in the catabolism of nucleotide precursors and loss of total purine content with reperfusion. These observations indicate that right ventricular myocardium is as equally sensitive to ischemic and reperfusion injury as left ventricular myocardium, and metabolic recovery from injury is equally prolonged.

Adenine Nucleotides↗
PubMed1986

Predicting outcome in coronary disease. Statistical models versus expert clinicians.

To study the accuracy with which long-term prognosis can be predicted in patients with coronary artery disease, prognostic predictions from a data-based multivariable statistical model were compared with predictions from senior clinical cardiologists. Test samples of 100 patients each were selected from a large series of medically treated patients with significant coronary disease. Using detailed case summaries, five senior cardiologists each predicted one- and three-year survival and infarct-free survival probabilities for 100 patients. Fifty patients appeared in multiple samples for assessing interphysician variability. Cox regression models, developed using patients not in the test samples, predicted corresponding outcome probabilities for each test patient. Overall, model predictions correlated better with actual patient outcomes than did the doctors' predictions. For three-year survival, rank correlations were 0.61 (model) and 0.49 (doctors). For three-year infarct-free survival predictions, correlations with outcome were 0.48 (model) and 0.29 (doctors). Comparisons by individual doctor revealed Cox model three-year survival predictions were better than those of four of five doctors (model predictions added significant [p less than 0.05] prognostic information to the doctor's predictions, whereas the converse was not true). For infarct-free survival, the Cox model was superior to all five doctors. Where predictions were made by multiple doctors, the interphysician variability was substantial. In coronary artery disease, statistical models developed from carefully collected data can provide prognostic predictions that are more accurate than predictions of experienced clinicians made from detailed case summaries.

Coronary Disease↗
PubMed1986

Dynamic right ventricular dimension. Relation to chamber volume during the cardiac cycle.

Whereas the left ventricle has been analyzed extensively, the apparent complexity of right ventricular geometry and contraction has hindered analysis of right ventricular performance by an assessment of instantaneous ventricular dimensions and volume during the cardiac cycle. To address this issue, we examined the temporal and quantitative relation between dynamic right ventricular free wall dimension, rate of pressure development (dP/dt), and pulmonary artery flow in the open-chest dog. Right ventricular free wall chord dimension was recorded by sonomicrometry, right ventricular pressure by micromanometer-tipped catheter, and pulmonary flow by electromagnetic probe. The point of peak positive right ventricular dP/dt closely correlated with the end of isovolumic contraction and initiation of ejection, occurring within 10 +/- 25 msec of initiation of pulmonary flow. Right ventricular dimension at peak positive dP/dt differed from dimension at initiation of chord shortening by less than 3%. Peak negative dP/dt correlated with end ejection, occurring within 10 +/- 25 msec of cessation of pulmonary flow. Right ventricular dimension at peak negative dP/dt differed from minimal dimension by less than 1%. In all dogs, volume ejected from the right ventricular chamber during each cardiac cycle was directly related to the change in right ventricular dimension during the same period (mean r = 0.969). This relationship between right ventricular stroke volume and dimensional change remained linear and was not changed (p = NS) by increases in right or left ventricular afterload induced by constricting the pulmonary artery or descending aorta. Right ventricular stroke work, calculated as the integral of instantaneous right ventricular pressure and dimension, correlated well (mean r = 0.980) with directly measured global right ventricular stroke work over a wide range; it was also not changed (p = NS) by changes in afterload. Accurate assessments of beat-to-beat right ventricular chamber volume and stroke work can be obtained by analysis of dynamic right ventricular chord dimension.

Animals↗
PubMed1986

The efficacy of blood versus crystalloid coronary sinus cardioplegia during global myocardial ischemia.

The efficacy of blood and crystalloid retrograde cardioplegia in protecting the ischemic myocardium was compared. Seventeen dogs underwent 2 hr of global myocardial ischemia while on cardiopulmonary bypass. Crystalloid (in nine dogs) or blood (in eight dogs) cardioplegic solution was infused continuously into the coronary sinus. Left and right ventricular function were assessed before ischemia and after 30 and 60 min of reperfusion by means of highly sensitive, load-independent index of contractility (the slope of the stroke work vs end-diastolic length relationship). Ventricular biopsies for ATP determination were obtained before ischemia, at the end of ischemia, and after 60 min of reperfusion. Left and right ventricular function returned to normal after 60 min of reperfusion in both groups. Left ventricular ATP remained unchanged, whereas small but significant decreases in right ventricular ATP were observed after 60 min of reperfusion in both groups. Thus continuous crystalloid or blood retrograde coronary sinus cardioplegia in dogs preserved myocardial function and metabolism equally well after 2 hr of global cardiac ischemia.

Adenosine Triphosphate↗
PubMed1985

Central retinal artery occlusion during cardiac catheterization.

A massive embolus of the central retinal artery occurred during cardiac catheterization and selective coronary angiography. Anterior chamber paracentesis and coughing resulted in restoration of retinal blood flow and vision within two hours. In two other cases retinal arteriolar embolization was observed in patients who had minimal or no ocular symptoms after cardiac catheterization.

Aged↗
PubMed1983

Transitional blood flow zones between ischemic and nonischemic myocardium in the awake dog. Analysis based on distribution of the intramural vasculature.

The present study evaluates the transitional or border zone of intermediate blood flow reduction between nonischemic and ischemic regions after acute coronary artery occlusion in chronically instrumented dogs, using methods that minimize an admixture of ischemic and nonischemic myocardium in the tissue analyzed. The regions perfused by occluded and nonoccluded vessels were identified by tracing the extra and intramural distribution of the coronary vasculature from postmortem angiograms. Regional blood flow was evaluated in serial 3-mm-wide epicardial and endocardial zones from outside and inside the interface between occluded and nonoccluded vessels. The zone of intermediate reduction in blood flow between nonischemic and ischemic regions occurred in the first 3-mm section immediately inside the region supplied by the occluded vasculature. Mean blood flow in this region was reduced to 58 +/- 6% and 61 +/- 5% (+/- SEM) of nonischemic region blood flow at the lateral and medial epicardial margins, respectively, and 47 +/- 5% and 45 +/- 6% at the lateral and medial endocardial margins, respectively. In the remaining ischemic zone, significant differences in blood flow existed between epicardial and endocardial layers; these differences were highly variable between animals. The data indicate that when the analysis of regional blood flow following acute ischemia is based on the anatomic distribution of the coronary vasculature, the transitional or border zone of intermediate reduction in blood flow is limited to a narrow zone immediately inside the occluded vasculature. Studies performed in acutely anesthetized dogs in which the occluded region was perfused via a two-chamber blood reservoir that allowed maintenance of perfusion and exclusion of microspheres from the circumflex region indicate that intermediate reductions in blood flow at the border of the ischemic zone resulted from an admixture of normal myocardium and, thus, do not represent a border zone of intermediate ischemia.

Animals↗
PubMed1978

The clinical significance of bundle branch block complicating acute myocardial infarction. 1. Clinical characteristics, hospital mortality, and one-year follow-up.

To provide an understanding of the clinical characteristics of patients with acute myocardial infarction (MI) and bundle branch block, experience from five centers was accumulated. Patients in whom bundle branch block first appeared after the onset of cardiogenic shock were excluded. In 432 patients, the most common types of block were left (38%) and right with left anterior fascicular block (34%). In 42% of the patients, bundle branch block was new. Progression to high degree (second or third degree) atrioventricular (AV) block via a Type II pattern occurred in 22% of the patients. Hospital and first year follow-up mortality rates were 28% and 28%, respectively. Only 46% of the patients developed pulmonary edema or shock (Killip Class III or IV), and hospital mortality was related to the amount of heart failure (8%, 7%, 27%, 83% for Killip Classes I-IV, respectively). Patients with progression to second degree or third degree AV block via a Type II pattern had increased hospital mortality compared with patients without this complication (47% vs 23%, P less than 0.001). In the absence of pulmonary edema or shock, patients with Type II second degree or third degree AV block still had a higher mortality rate than patients without advanced AV block (31% vs 2%, P less than 0.005), with nearly all the deaths due to abrupt development of AV block. Thus, in many patients MI with bundle branch block is associated with severe heart failure. However, this was not true for a majority of the patients, in whom therapy aimed at preventing morbidity and mortality due to the bradyarrhythmia of advanced AV block might be beneficial.

Acute Disease↗
PubMed1978

The clinical significance of bundle branch block complicating acute myocardial infarction. 2. Indications for temporary and permanent pacemaker insertion.

The indication for prophylactic temporary and permanent pacing during acute myocardial infarction (MI) complicated by bundle branch block is high risk of progression via a Type II pattern to second or third degree (high degree) AV block during hospitalization or follow-up. In this study, determinants of high degree AV block during hospitalization and sudden death or recurrent high degree block during the first year of follow-up were examined in 432 patients with MI and bundle branch block. Timing of onset of bundle branch block, the involved fascicles, and the PR interval were examined as determinants of risk of progression to high degree AV block during MI. At highest risk were 186 patients with blocks involving the right bundle and at least one fascicle of the left bundle which were not documented on prior electrocardiograms. Risk was similar with (38%) or without (31%) accompanying first degree AV block. Patients with transient high degree AV block during MI had a 28% incidence of sudden death or recurrent high degree block during the first year of follow-up. Patients not continuously paced had a higher incidence of sudden death or recurrent high degree block than patients continuously paced (65% vs 10%, P less than 0.001). Sudden death during follow-up also occurred in 13% of patients without high degree block during MI. A subgroup with 1) documented prior MI, 2) anterior or indeterminant acute MI, and 3) no symptoms of cardiac failure had a 35% risk of sudden death. The role of permanent pacing in this group is unknown. Thus, patients at high risk of high degree AV block should receive prophylactic temporary pacing. Patients who survive high degree block with MI should receive temporary and then permanent pacing. Patients without high degree AV block during MI who nervertheless have a high risk of sudden death may benefit from permanent pacing.

Adult↗
PubMed1976

Patient-initiated rapid atrial pacing to manage supraventricular tachycardia.

Patient-controlled rapid atrial pacing was used to manage 12 cases of recurrent supraventricular tachycardia refractory to drug therapy. The pacing system consists of an implanted receiver-lead system and an external patient-activated transmitter. In each case, brief periods (5 to 20 seconds) of rapid atrial pacing were effective in terminating the supraventricular tachycardia and resulted in a return to normal sinus rhythm. In three patients, occasional transient episodes of atrial flutter or atrial fibrillation preceded a spontaneous return to normal sinus rhythm. The pacing system was removed in one patient 13 months postoperatively because of persistent pericarditis; one patient died of an unrelated cerebral hemorrhage 13 months postoperatively. Successful management of supraventricular tachycardia has been maintained in the 10 remaining patients for 15 to 36 months (average 26.4). In more than 6,000 patient applications of rapid atrial pacing, there has been only one failure to convert the tachycardia. Successful application of permanent rapid atrial pacing requires (1) prescreening of patients with temporary external rapid atrial pacing to verify susceptibility to conversion of supraventricular tachycardia and absence of anomalous conduction pathways that may permit conduction of rapid pacing rates to the ventricles, and (2) assessment of the patient's ability to use the transmitter properly.

Adult↗
PubMed1975

Comparison of sisomicin and gentamicin in bacteriuric patients with underlying diseases of the urinary tract.

Sisomicin and gentamicin (2 mg/kg) were administered in a random fashion to patients with bacteriuria superimposed on abnormalities of the urinary tract. Cure was achieved in a similar number of patients in both groups, but superinfection and reinfection with resistant microorganisms was more frequent in patients receiving gentamicin. Untoward side effects were not frequent in this series, especially if the serious underlying urological disease of most patients is taken into consideration. The susceptibility of the causative pathogens to the antibiotic administered and the severity of the underlying disease were the most important factors in the outcome.

Anti-Bacterial Agents↗
PubMed1975

A new information system for medical practice.

A data bank containing our clinical experience with more than 3,000 patients with suspected and documented ischemic heart disease is being used to expand our ability to care for patients. This report describes how the experience is documented, stored, and retrieved so that it can be used in patient management. Data acquisition is integrated with patient care by means of forms that are part of the patient record. Follow-up information is obtained at six months, one year, and yearly thereafter. All data are stored in a computer information system that allows the doctor to recall the experience of patients like his new patient. Prognostic information is available on each new patient both on-line and in the form of a printed laboratory report. The data bank represents an initial chapter of a computer textbook of medicine.

Beta Particles↗