Search PubMed⌕ Search

Biomedical subjects

M L Jacobs

Publications and source records attributed to M L Jacobs.

At least 73 records · Page 4Linked to original sources
PubMed1987

Augmentation of pulmonary blood flow by a right atrial balloon pump after the Fontan operation.

The Fontan principle of right ventricular exclusion is frequently applied to complex congenital lesions. Results are adversely affected by increases in pulmonary vascular resistance and/or ventricular end-diastolic pressure. Survival depends on means to increase pulmonary blood flow. To address this problem, we have developed a triple-balloon catheter that is passed via the femoral vein to the right atrium. Inflation is sequenced so that small balloons located at the junction of each vena cava with the atrium inflate first. Then the larger central balloon inflates, ejecting blood from the right atrium to the pulmonary arteries. The pump is timed to inflate during ventricular systole. In this study, we tested the catheter in vivo in eight dogs. Tricuspid atresia was created and right ventricular exclusion accomplished. Pulmonary blood flow was measured with a flow probe in the right atrium-to-pulmonary artery conduit, at central venous pressures of 15, 20, and 25 mm Hg. Pulmonary blood flow was increased by balloon pumping in every instance (p less than .05). Maximal augmentation of pulmonary blood flow (25.5%) was achieved at a central venous pressure of 15 mm Hg with a balloon ratio of 1:2. Less augmentation was achieved at a central venous pressures of 20 mm Hg (8.4% to 13.0%) and a 25 mm Hg (4.4% to 5.3%) and at balloon ratios of 1:4 and 1:8. We conclude that (1) a triple-balloon pump in the right atrium can significantly augment pulmonary blood flow after right ventricular exclusion and (2) most effective augmentation can be achieved without excessive volume loading. Pulsatile augmentation of pulmonary blood flow with this device should improve survival after Fontan operations.

Animals↗
PubMed1986

Surgical management of postinfarction ventricular septal rupture.

Recognition and treatment of patients with ventricular septal rupture following infarction have improved over the past 25 years to the extent that survival with good long-term palliation is achieved in the majority of patients treated surgically for this catastrophic complication of acute myocardial infarction. The small minority of patients who, by the process of selection, are seen for surgical correction of septal rupture several weeks after infarction routinely have repair of the septal defect with an operative risk of less than 10%. With increasingly early diagnosis of septal rupture, the majority of patients are seen for consideration of surgical repair often within hours after septal rupture. Most such patients seen early after septal rupture exhibit cardiogenic shock. Refinement of operative techniques both for suture repair of freshly infarcted myocardium and for repair of defects in different anatomical locations has markedly improved survival in these critically ill patients. Deferral of operation for the patient in cardiogenic shock after septal rupture represents a failed therapeutic strategy. Conversely, emergency operation for the patient with septal rupture and cardiogenic shock has markedly improved survival in this high-risk group. Prolonged intraaortic balloon pump support and deferred operation should be reserved for the uncommon patient who, because of delayed diagnosis or referral, is seen in an advanced stage of multisystem failure in which the risks of early operative intervention involve the function of organs other than the heart.

Female↗
PubMed1982

Regional myocardial radiotracer kinetics in dogs using miniature radiation detectors.

An implantable device for continuous measurement of regional myocardial radioisotope activity was designed and validated. The probe consists of a 2-mm3 cadmium telluride crystal surrounded by lead foil housed in a 4.5-mm outer diameter steel cylinder. Activity in serial dilutions of thallium-201 measured by this miniature gamma detector correlated well with activity measured in the well counter (r = 0.99). In vivo probe measurements of regional myocardial thallium-201 activity in a canine model were compared with activity in punch biopsies, again with excellent correlation (r = 0.90). The crystal was mounted on a modified arterial clamp, which was inserted into the left ventricle through, the apex and situated on the endocardial surface of the anterior or posterior wall. It was thus possible to measure regional isotope activity without excessive background from the blood pool and opposite heart wall. The probe was found best suited for monitoring activities of isotopes with energies between 60 and 250 keV. With a pair of these devices, dynamic studies of the myocardial kinetics of radioisotopes such as thallium-201 in normal and ischemic myocardium are now possible.

Animals↗
PubMed1981

Relation between ionized calcium concentration and ventricular pump performance in the dog under hemodynamically controlled conditions.

The effect of plasma ionized calcium concentration on left ventricular function was studied in the canine heart on right heart bypass. Stroke volume, mean arterial pressure and heart rate were controlled. Plasma ionized calcium was lowered to 0.58 +/- 0.01 mM by citrate infusion and raised to 1.70 +/- 0.01 mM by calcium chloride infusion in random order in each dog. Left ventricular function at each of these ionized calcium levels was compared with that in an immediately preceding normocalcemic period. At a constant stroke work (16.9 +/- 0.2 g-m), sustained hypercalcemia was associated with a small decrease in left ventricular end-diastolic pressure (1.7 +/- 0.7 cm H2O, p less than 0.05) despite a marked increase in peak left ventricular dP/dt (first derivative of ventricular pressure) averaging 34 percent (p less than 0.001). Coronary blood flow, tension-time index and myocardial oxygen consumption were not significantly altered. Stroke work determined at a left ventricular end-diastolic pressure of 14 cm H2O, by interpolation in left ventricular function curves, was 11 +/- 4.4 percent above that at control normocalcemia (p less than 0.05). At a constant stroke work (16.9 +/- 0.2 g-m), sustained hypocalcemia was associated with a marked depression of left ventricular function as demonstrated by a substantial increase (from 4.9 +/- 0.3 to 12.7 +/- 1.1 cm H2O, p less than 0.0001) in left ventricular end-diastolic pressure (p less than 0.0001), decreased mean systolic ejection rate (p less than 0.01) and decreased peak left ventricular dP/dt (p less than 0.0001). Coronary blood flow increased (p less than 0.05) whereas myocardial oxygen consumption did not change significantly. A marked displacement of left ventricular function curves to the right (compared with curves obtained during normocalcemia) was observed, and stroke work determined at a left ventricular end-diastolic pressure of 14 cm H2O was 52 +/- 5.4 percent below control level (p less than 0.001). It appears that hypercalcemia, when initiated from a normal control level, provides only a small enhancement of ventricular pump performance (as indexed by the stroke work-left ventricular end-diastolic pressure relation) despite a marked increase in peak left ventricular dP/dt, whereas marked improvement of left ventricular performance may be expected when calcium infusion is initiated from an ionized calcium level that is below normal.

Animals↗
PubMed1981

Regional myocardial protection during aortic cross-lamp ischemia in dogs: calcium-containing crystalloid solutions.

To study the effects of calcium in cardioplegic solutions, an in situ dog heart model was used that allowed infusion of two different cardioplegic solutions into separate regions of the same heart. Two concentrations of ionized calcium, 1.0 mM and 0.5 mM, in a cold, potassium-containing solution were tested in two groups of dogs and compared with the same cold, potassium-containing solution but without the calcium, during 100 minutes of global myocardial ischemia induced by aortic clamping. Results were evaluated in terms of percent change of regional systolic shortening measured with ultrasonic piezoelectric crystals, percent change of regional myocardial blood flow, and change of regional left ventricular myocardial diastolic distensibility. No significant differences were found between myocardial regions protected with calcium of either concentration and regions protected with calcium of either concentration and regions protected without calcium. This study could demonstrate no beneficial or adverse effects of including calcium in this type of crystalloid cardioplegic solution applied to an in situ dog heart model.

Animals↗
PubMed1981

Right ventricular distension and left ventricular compliance.

The constraint of the right ventricle (RV) on the end-diastolic pressure-volume (PV) relationship of the nonischemic and ischemic left ventricle (LV) was studied. The model used was the isovolumic beating LV, with separately perfused ejecting RV with controlled RV distension. The effect of augmented RV distension on the nonischemic LV PV relationship was examined. A change from mild [right ventricular end-diastolic pressure (RVEDP) = 1.5 mm Hg] to severe (RVEDP = 16 mmHg) RV distension resulted in a significant leftward shift of the LV PV relationship. Ischemia was produced for 90 min by reducing flow in the cannulated left main coronary artery and the effect of two levels of stable RV distension on the PV relationship of the ischemic LV was examined. Mild RV distension and moderate (RVEDP = 6 mmHg) RV distension were used. In both groups, there was a progressive leftward shift in the LV PV relationship that was significant by 60 min of ischemia. No change was seen in nonischemic controls. Ventricular relaxation, as described by the time constant of isovolumic relaxation, T, was impaired throughout ischemia but was not sufficiently prolonged to explain the above changes. Thus, the time course of change in the LV PV relationship during ischemia differs from that previously reported after pacing-induced ischemia in humans. Neither the external constraint of the RV nor incomplete relaxation explains this difference.

Animals↗
PubMed1980

Aortic valve replacement: a 9-year experience.

Experience with aortic valve replacement over a 9-year period is reviewed. Hospital mortality was 5.0%, with an additional late mortality of 15.0% during a mean follow-up period of 4.3 years. There was a 7.5% mortality among the 93 patients who were operated on using direct coronary perfusion. There were no early deaths among the 48 patients operated on using cold cardioplegic arrest. Paravalvular leaks developed in 20 patients, and 9 had reoperation. There were no early deaths following elective reoperations for prosthetic valve dysfunction, but urgent reoperation was associated with a 40% mortality. Eighty percent of all patients are still alive at a maximum follow-up of 9 years. Eighty-six percent of the survivors who were in New York Heart Association Functional Class III or IV before operation are now in Class I or II. Hypothermic cardioplegic arrest was found to be preferable to coronary perfusion as a method of myocardial protection during aortic valve replacement. Patients with paravalvular leaks who have a history of left ventricular failure prior to aortic valve replacement should be considered candidates for early elective reoperation, owing to the significantly greater mortality associated with urgent reoperation.

Adolescent↗
PubMed1980

Late graft patency and symptom relief after aorta-coronary bypass.

One hundred six consecutive patients underwent elective or emergency coronary artery bypass grafting (CABG) between January, 1974, and November, 1975. There were 90 men of an average age of 54 years and 16 women an average of 64 years. Unstable angina (preinfarction angina, angina decubitus, and crescendo angina) was present in 54 patients of this group and eight were in congestive heart failure. Sixty-two of the 106 had previously had myocardial infarctions and four had evolving infarctions. There were four operative deaths (3.8%) and one early hospital death (less than 30 days' hospitalization). Perioperative infarction occurred in five of the survivors. Of the 197 grafts placed in the 101 survivors, 94% were patent by angiography at 1 to 2 weeks (175 of 187 vein grafts and 10 of 10 left internal mammary grafts). At 1 to 2 years after CABG, 62% of the survivors consented to repeat angiography at which time 94% of the grafts were patent (101 of 108 vein grafts and seven of seven left internal mammary grafts). Clinical follow-up of 81 of the 101 survivors at 1 year found 99% of them to be asymptomatic or improved. Repeat clinical follow-up of all survivors (99 of 101) at 3 to 4 years found 93.9% asymptomatic or improved. Overall survival, including operative deaths, was 92.4% at 4 years.

Adult↗
PubMed1980

Regional myocardial protection: use of a new method to compare cold potassium cardioplegia with hypothermic coronary perfusion.

A new canine model was developed to compare two cardiplegic agents using each heart as its own control. Paired piezoelectric crystals were implanted into the left anterior descending and circumflex regions. The percentage of shortening (systolic shortening/end-diastolic segment length X 100) was assessed in each region on right-heart bypass over a range of cardiac outputs. Durng 100 minutes of ischemic arrest the left anterior descending and circumflex regions were perfused separately every 20 minutes with either cold buffered saline or cold KCl cardioplegia solutions. After recovery, the percentage of shortening after ischemic arrest was determined. The percentage of shortening in the region protected by KCl was unchanged (12.5 +/- 5.0 to 13.0 +/- 4.6%) after arrest, but was markedly decreased in the buffered saline region (11.3 +/- 5.9 to 3.2 +/- 4.9%) (p < 0.001, n = 6). This model should facilitate the comparison of two cardioplegic solutions.

Animals↗
PubMed1977

Acute pancreatitis: analysis of factors influencing survival.

Of patients with acute pancreatitis (AP), there remains a group who suffer life-threatening complications despite current modes of therapy. To identify factors which distinguish this group from the entire patient population, a retrospectiva analysis of 519 cases of AP occurring over a 5-year period was undertaken. Thirty-one per cent of these patients had a history of alcoholism and 47% had a history of biliary disease. The overall mortality was 12.9%. Of symptoms and signs recorded at the time of admission, hypotension, tachycardia, fever, abdominal mass, and abnormal examination of the lung fields correlated positively with increased mortality. Seven features of the initial laboratory examination correlated with increased mortality. Shock, massive colloid requirement, hypocalcemia, renal failure, and respiratory failure requiring endotracheal intubation were complications associated with the poorest prognosis. Among patients in this series with three or more of these clinical characteristics, maximal nonoperative treatment yielded a survival rate of 29%, compared to the 64% survival rate for a group of patients treated operatively with cholecystostomy, gastrostomy, feeding jejunostomy, and sump drainage of the lesser sac and retroperitoneum.

Acute Disease↗
PubMed1975

Composite implants for orthopedic applications: in vivo evaluation of candidate resins.

Three resins which include poly (methyl methacrylate), surgical Simplex P, and ultrahigh molecular weight polyethylene were selected to be evaluated as candidate systems for a polymer based composite for hard tissue prosthesis. Characterization of the mechanical behavior of these polymers in different environments including in vitro and in vivo storage was accomplished. As a result, conclusions were made as to which material maintained the least amount of mechanical variance as influenced by environmental effects. In vivo studies of implanted materials provided for a study of soft tissue response to each material. Conclusions were then developed as to the varying degrees of tissue reaction initiated by each material, and which resin generated the greatest tissue response with respect to the others.

Animals↗