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Biomedical subjects

H M Spotnitz

Publications and source records attributed to H M Spotnitz.

At least 73 records · Page 4Linked to original sources
PubMed1991

Effect of AICD patch electrodes on the diastolic pressure-volume curve in pigs.

Although the automatic implantable cardioverter defibrillator (AICD) is effective against malignant ventricular arrhythmias, the effects of AICD patches on left ventricular diastolic properties have not been defined. Accordingly, extrapericardial (group E, n = 5) or intrapericardial (group I, n = 6) AICD patches were implanted through a median sternotomy in 11 anesthetized pigs. Six weeks later, using a left thoracotomy, the hearts were arrested with hypothermic cardioplegia. A balloon catheter was inserted into the left ventricle through the aortic root, and pressure-volume curves were measured before and after sequential removal of patches and pericardium. A dense intrapericardial fibrotic reaction in group I was not present in group E. Normalized left ventricular filling volumes in group E were significantly larger at pressures of 5.1 to 10, 15.1 to 20, and 20.1 to 28 mm Hg compared with group I (p less than 0.05). We conclude that intrapericardial AICD patches adversely affect left ventricular diastolic pressure-volume relations and recommend that AICD patches be placed in the extrapericardial location clinically whenever possible.

Animals↗
PubMed1991

Transvenous pacemakers in children: relation of lead length to anticipated growth.

Although transvenous pacing is feasible in infants and children, uncertainty remains as to how to allow for future growth at the time of lead insertion. Accordingly, we retrospectively reviewed the relation between age and transvenous lead length. Standard posteroanterior chest roentgenograms were reviewed for 26 patients with transvenous pacemakers inserted at Babies Hospital and Presbyterian Hospital between 1985 and 1989. Sixteen of these were children (age range, 0.75 to 15 years) and 10 were adults (age range, 27 to 90 years). The intravascular length of right ventricular pacing leads was measured as projected on the roentgenogram. In 10 children, the presence of lead loops in the right atrium required the lead length that would have resulted from conventional placement to be estimated. Results for right ventricular pacing lead lengths were correlated with age using linear regression analysis. Average uncorrected lead length measured on the roentgenogram was 345 +/- 35 mm (standard deviation) in adults and 222 +/- 51 mm in children. The use of right atrial loops increased implanted lead length by an estimated 79 mm, from 188 +/- 26 to 267 +/- 43 mm. The difference between lead length in children and adults was analyzed. Approximately 190 mm of additional right ventricular pacing lead in infants and 100 mm in 10-year-old children was needed for growth to adult size. We conclude that an 80-mm right atrial lead loop will allow 6 to 12 years (mean, 8 years) of growth in infants and children without the need for reoperation to adjust lead length.

Adolescent↗
PubMed1990

Transvenous pacing in infants and children with congenital heart disease.

A technique for transvenous pacemaker implantation in children with complex heart disease is described. The use of small positive-fixation leads, introducers, retained guidewires, and atrial lead loops to allow for growth all have an important role in management of this often challenging problem.

Cardiac Catheterization↗
PubMed1990

Simulated left ventricular aneurysm and aneurysm repair in swine.

Patch reconstruction of left ventricular aneurysm may be superior to linear closure, but this hypothesis has not been tested experimentally. Accordingly, six anesthetized domestic pigs were instrumented to measure regional left ventricular wall thickening, stroke volume, systolic left ventricular pressure, and myocardial oxygen consumption. With total bypass and cardioplegia, a 6 by 8 cm Dacron patch was inserted into the anteroapical left ventricle. Simulations were as follows: left ventricular aneurysm, patch open; patch reconstruction, 50% patch plication; standard repair, ventriculotomy edges approximated. Global function, from stroke work (stroke volume x integral of left ventricular pressure)-left ventricular end-diastolic pressure curves, was depressed in all three simulations compared with control. A tendency for stroke work to be greater for standard repair than for left ventricular aneurysm and patch reconstruction at higher preloads was not statistically significant. Mechanical efficiency, from stroke work/myocardial oxygen consumption (joules per milliliter oxygen per beat), was 2.43 +/- 0.52 (mean +/- standard error of the mean) (control), 2.22 +/- 0.94 (standard repair), 1.27 +/- 0.39 (patch reconstruction), and 1.09 +/- 0.37 (left ventricular aneurysm) (no significant differences). Regional work was calculated as regional left ventricular wall thickening x integral of left ventricular pressure. The slope of the regional work-end-diastolic wall thickness relation decreased in the posterior wall 14.0 +/- 2.9 (control) versus 8.4 +/- 2.0 (left ventricular aneurysm), 6.9 +/- 1.4 (patch reconstruction), and 7.4 +/- 1.4 (standard repair) (p less than 0.05). In the anterior wall, contractility did not change significantly (7.4 +/- 1.2, control; 7.8 +/- 2.7, left ventricular aneurysm; 5.0 +/- 0.4, patch reconstruction; and 5.3 +/- 0.4, standard repair). Decreased end-diastolic wall thinning anteriorly suggested tethering. These results in the normal left ventricle suggest that patch ventriculoplasty is of no greater benefit than linear repair. Either repair may impede function of adjacent myocardium through restriction of regional diastolic lengthening.

Animals↗
PubMed1989

Long-term function of human cardiac allografts assessed by two-dimensional echocardiography.

Previous studies from our laboratory demonstrated increasing left ventricular mass in cyclosporine-treated cardiac allograft recipients over 30 days after transplantation, but the long-term evolution of this process and possible effects on allograft function are unknown. Accordingly, quantitative two-dimensional echocardiography was performed 2 and 23 days and 15 months postoperatively in 14 recipients treated with cyclosporine and prednisone. Changes in left ventricular ejection fraction, end-diastolic volume, mass, and end-systolic wall stress were analyzed. Comparison of studies at 2 and 23 days revealed significant (p less than 0.01) increases in ejection fraction (54% +/- 8% [standard deviation] to 62% +/- 4%), end-diastolic volume (84% +/- 32 ml to 96 +/- 31 ml), and left ventricular mass (118 +/- 45 gm to 136 +/- 41 gm). Comparison of studies at 23 days and 15 months revealed no significant change in end-diastolic volume or left ventricular mass, whereas ejection fraction decreased slightly (62% +/- 4% to 57% +/- 4%, p less than 0.01). End-systolic wall stress decreased when data at 2 days and 15 months were compared (83 +/- 24 gm/cm2 versus 66 +/- 18 gm/cm2, p less than 0.05), but no change in contractility was apparent from the ejection fraction/end-systolic stress relation. We conclude that left ventricular mass and end-diastolic volume increase early after transplantation in cyclosporine-treated cardiac allograft recipients, but these changes are not predictive of long-term results, which are characterized by no significant late variation in left ventricular mass, end-diastolic volume, or contractility.

Adolescent↗
PubMed1988

Effect of electrophysiological testing on ejection fraction during cardioverter/defibrillator implantation.

To evaluate the effect of repeated induction of ventricular tachycardia or ventricular fibrillation, or both, in patients with poor left ventricular function, we performed intraoperative two-dimensional echocardiography in 6 patients undergoing implantation of the automatic implantable cardioverter/defibrillator. Changes in left ventricular ejection fraction in sinus rhythm were assessed before the first inducible ventricular arrhythmia and after a mean of 6 +/- 1.9 (SD) episodes of ventricular tachycardia or ventricular fibrillation. During the procedure no significant change in mean ejection fraction was observed (28 +/- 14 versus 27 +/- 17%). Only 1 of the 6 patients studied had a change in ejection fraction greater than 3% (a decrease from 20 to 11%). In an overall clinical series of 38 primary implants or generator changes (including electrophysiological testing) in 29 patients, 1 patient recovered after postoperative inotropic support and 1 died of acute postoperative ischemic heart failure. We conclude that ventricular arrhythmias induced during automatic implantable cardioverter/defibrillator implantation have no immediate deleterious effects on ejection fraction in most patients with compromised left ventricular function and without ongoing ischemia.

Aged↗
PubMed1988

Effects of simulated intraoperative electrophysiological testing on function of the canine left ventricle.

With the increasing application of arrhythmia surgery, intraoperative electrophysiological study is done frequently, although its potential to cause acute depression of cardiac function remains unresolved. This study examines the acute effects of simulated electrophysiological testing on left ventricular function. Seven dogs were anesthetized with sodium pentobarbital and instrumented for measurement of heart rate, mean aortic pressure, cardiac output (CO), and systemic vascular resistance (SVR). Systolic pressure-dimension work loops were analyzed over varying preloads. Contractility was assessed from the end-systolic pressure-dimension relationship (Ees) and from preload recruitable stroke work (PRSW). After the collection of control data, electrophysiological testing was simulated by pacing at 200 beats per minute for 30 seconds, fibrillating for 15 seconds, and finally defibrillating with a 10-J countershock. Data were recorded after 3 and 6 simulations of ventricular fibrillation (VF3, VF6). Mean heart rate and mean aortic pressure did not vary significantly during the course of the experiment. CO decreased from a control value of 2.7 +/- 0.2 L/min (+/- the standard error of the mean) to 2.0 +/- 0.1 (p less than 0.05) after VF3 and remained significantly depressed after VF6. SVR increased from a control value of 3,231 +/- 211 dyne sec cm-5 to 3,976 +/- 305 dyne sec cm-5 after VF3 (p = not significant) and increased further to 4,774 +/- 442 dyne sec cm-5 after VF6 (p less than 0.05). Neither Ees nor PRSW varied significantly even after 6 EP simulations, thereby indicating that contractility was unchanged during the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Quantitative analysis of regional systolic function with left ventricular aneurysm.

Left ventricular aneurysm (LVA) remains a poorly understood entity, often resulting in congestive failure that is not consistently improved by standard resection with linear closure. Although other surgical approaches have been proposed, current methods to assess their effect on left ventricular function are not adequate. The purpose of the present study was to quantitatively define regional systolic function in patients with LVA and to assess acute changes in regional function after standard repair. Seven patients underwent resection of an anteroapical LVA. Intraoperative two-dimensional echocardiography was performed off cardiopulmonary bypass immediately before and after resection. In all patients, short-axis views at the papillary muscle (apex) level showed anteroseptal paradox and distorted geometry, whereas at the mitral valve (base), symmetric wall motion and geometry were preserved. Videotaped echo images were divided into octants by a floating axis fitted to internal landmarks. Myocardial area and midwall perimeter were obtained for each octant, and wall thickness was calculated at end diastole (ED), isovolumetric systole (IS), and end systole (ES). Wall thickening (delta t) for each segment was calculated as the percent increase in thickness from ED and averaged for all seven patients. At the apex level before resection, isovolumetric thinning occurred in the aneurysm as well as bordering segments, with delta t ranging from -17 +/- 5% (+/- SEM) in the anteroseptal segment to 12 +/- 6% posterolaterally (p less than 0.05). The isovolumetric bulge was followed by late-systolic thickening, however, with delta t ranging from 13 +/- 7% to 27 +/- 8% (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Controlled reperfusion following regional ischemia.

The ability to reverse acute coronary occlusion with fibrinolytic agents and percutaneous transluminal angioplasty has increased interest in the revascularization of ischemic myocardium. This study defines changes in global ventricular function, mass, and compliance during acute coronary occlusion and following reperfusion with blood in the beating and arrested heart. In 17 dogs on cardiopulmonary bypass, the proximal left anterior descending coronary artery was occluded for 45 minutes. In 12 dogs, flow was reestablished by releasing the coronary snare in the beating heart. In the other 5 dogs, the snare was released during a continuous 10-minute infusion of blood potassium cardioplegia in the arrested heart. Coronary occlusion resulted in significant decreases in stroke work index and left ventricular (LV) mass, but compliance was unchanged. Reperfusion in the beating heart increased LV mass compared with the values measured before ischemia (104 +/- 5 versus 95 +/- 5 gm; p less than 0.05) and decreased LV compliance (39 +/- 4 versus 53 +/- 4 ml at LV end-diastolic pressure of 8 mm Hg; p less than 0.05). In contrast, with blood cardioplegia-based reperfusion in the arrested heart, LV mass and LV compliance remained unchanged from control values. We conclude that revascularization of acutely ischemic myocardium in the beating heart further impairs LV function by increasing LV mass and decreasing compliance. This damage can be avoided by reperfusion with blood cardioplegia in the arrested heart.

Animals↗
PubMed1986

Phase analysis of gated blood pool scintigraphic images to localize bypass tracts in Wolff-Parkinson-White syndrome.

The ability of radionuclide techniques to localize bypass tracts in patients with Wolff-Parkinson-White syndrome to sites around the atrioventricular (AV) ring using a three view triangulation method was investigated. In 17 patients with Wolff-Parkinson-White syndrome, phase images were generated from gated blood pool scans using the first Fourier harmonic of the time-activity curve of each pixel. In addition, the difference between left and right ventricular mean phase angles was calculated for each patient and for 13 control subjects. Bypass tracts were localized to one or more sites on a 10 site grid schematically superimposed on the AV ring (Duke grid) by electrophysiologic study in all patients and by intraoperative mapping in 7 of the 17 patients. These same 10 anatomic sites were projected onto three scintigraphic views and the site of earliest ventricular phase angle was located in each view. The 10 sites around the AV ring were divided into two anatomic groups: free wall and septal/paraseptal. Phase image locations correlated with electrophysiologic locations within one grid site in 11 of 11 patients with free wall tracts and were confirmed at surgery in 5 of the 11. In five of six patients with septal/paraseptal tracts, electrophysiologic study could not localize the bypass tract to one site, whereas phase images localized two of the five as free wall adjacent to the septum, one as paraseptal and two as true posteroseptal. One posteroseptal site was confirmed at surgery. In one patient, in whom phase image analysis and electrophysiologic study showed different sites, existence of both tracts was confirmed at surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Compliance, mass, and shape of the canine left ventricle after global ischemia analyzed with two-dimensional echocardiography.

End-diastolic pressure (EDP)-volume (EDV) curves were constructed for the left ventricle (LV) in 10 dogs on cardiopulmonary bypass before and after 45 min of normothermic ischemic arrest. LVEDV and mass were calculated from three perpendicular two-dimensional echocardiographic sections using a Simpson's rule algorithm. The echocardiographic method employed was specially developed in earlier work for physiologic studies in dogs. Postmortem pressure-volume curves were measured for comparison by direct saline infusion into sealed ventricles. LVEDV was plotted against LVEDP (0-20 mm Hg) and data were analyzed by two-way analysis of variance and also by exponential curve fitting to the relation EDP = alpha e beta EDV, where beta is the derived exponential constant reflecting slope and thereby ventricular stiffness. Postischemic EDP-EDV curves shifted to the left and the beta constant increased (beta = 0.02 +/- 0.005 (SE) vs 0.05 +/- 0.01, P less than 0.05). LV eccentricity, the ratio between long- and short-axis measurements, was unchanged (1.43 +/- 0.05 vs 1.46 +/- 0.06 postischemia, NS), but LV mass increased (105 +/- 7 vs 128 +/- 9 g postischemia, P less than 0.001). Postischemic LV mass by echo was not significantly different from measured postmortem LV mass (r = 0.87). The nonparallel alteration in the EDP-EDV curves, lack of change in LV shape (eccentricity), and increase in LV mass in the postischemic ventricle suggest that increased ventricular stiffness rather than direct encroachment by the edematous endocardium on chamber volume is responsible for postischemic changes in LV diastolic properties.

Animals↗
PubMed1985

Hemostatic effectiveness of fibrin glue derived from single-donor fresh frozen plasma.

Fibrin glue derived from pooled human blood is an effective sealant for high-porosity vascular grafts and a valuable topical hemostatic agent in heparinized patients. Use of this agent in the United States is prohibited because of potential transmission of hepatitis B, acquired immunodeficiency syndrome, and other serologically transmitted illnesses. We have developed a cryoprecipitation technique that allows preparation of fibrin glue from single-donor fresh frozen plasma. Use of this agent presumably entails no greater risk of disease transmission than intravenous administration of single-unit fresh frozen plasma. This report describes our early clinical experience with this material. Fibrin glue was used as a sealant for porous woven Dacron tubular prostheses and cardiovascular patches in 19 patients. The fibrin glue sealant has also been employed to control bleeding from needle holes and small anastomotic tears in 22 patients. No patient in this series had a bleeding complication from a suture line or graft treated with fibrin glue. This experience indicates that like fibrin glue from pooled blood, fibrin glue from single-donor plasma is effective as a graft sealant and topical hemostatic agent. Preparation of fibrin glue from single-donor plasma is simple and economical, and may provide cardiothoracic surgeons in the United States with a widely available, valuable hemostatic adjunct.

Blood Donors↗
PubMed1985

Effects of simulated clinical cardiopulmonary bypass and cardioplegia on mass of the canine left ventricle.

Myocardial edema is a well-documented response to ischemia and reperfusion in dogs and can be detected as an increase in left ventricular (LV) mass measured echocardiographically. Investigation in human beings has failed to demonstrate similar increases in LV mass after routine cardiac operations. However, direct comparison of these observations is not possible, because dogs have not been studied under conditions of cardiopulmonary bypass (CPB) and global ischemia that rigorously reproduce those of a clinical operation. Accordingly, clinical CPB and global ischemia were simulated in 8 adult dogs. Multisection two-dimensional echocardiograms and a computerized light pen were used to calculate LV volume and mass. The data were analyzed during four periods: before CPB; CPB before cross-clamping; CPB after cross-clamping, and after CPB. Echocardiographic LV mass increased significantly from 89.5 +/- 7.4 gm (before CPB) to 94.6 +/- 8.5 gm (CPB before cross-clamping) (p less than 0.05) and from 94.6 +/- 8.5 gm to 100.4 +/- 8.1 gm (CPB after cross-clamping) (p less than 0.05). Overall, mass increased 13.9% (p less than 0.05). Mean wall thickness increased 0.08 cm (p less than 0.05) overall and correlated with the increase in mass (r = 0.79). Postmortem mass correlated well with late echocardiographic mass (r = 0.95). Interobserver correlation of 98 separate mass determinations was high (r = 0.84) with a coefficient of variation of 10.5%. We conclude that canine LV mass increases significantly with CPB and global ischemia maintained within clinical standards and that human beings and dogs may differ in extent of edema during CPB.

Animals↗
PubMed1985

Two-dimensional echocardiography in dogs. Variation of left ventricular mass, geometry, volume, and ejection fraction on cardiopulmonary bypass.

Quantitative two-dimensional echocardiography was evaluated in 39 open-chest dogs placed on cardiopulmonary bypass. The correlation coefficient of left ventricular end-diastolic volume against postmortem pressure-volume curves was r = 0.89 to 0.93 (347 measurements in 15 dogs, 0 to 24 mm Hg). Ejection fraction was validated against roller pump flow and echo left ventricular end-diastolic volume (r = 0.83, n = 13). Left ventricular mass in vivo was compared with postmortem left ventricular mass (r = 0.81 in 21 early studies, r = 0.91 in 10 later studies with updated equipment) and was found to increase with ischemic injury as well as cardiopulmonary bypass with hemodilution. Left ventricular mass increased (p less than 0.001) from 119 +/- 5 (standard error of the mean) to 138 +/- 6 gm (n = 23) after 2 1/2 hours on cardiopulmonary bypass and moderate hemodilution. With the addition of ischemic arrest, left ventricular mass increased from 119 +/- 7 to 148 +/- 11 gm (p less than 0.01, n = 8), and myocardial water content increased by 2.0% +/- 0.4%, which accounted for at least 65% of the observed mass change. Mean left ventricular wall thickness increased from 13.8 to 15.5 mm (p = 0.02) after ischemia. Ventricular shape became more spherical with increasing left ventricular end-diastolic pressure. We conclude that two-dimensional echocardiography can be reliably used for accurate, serial measurements in physiological studies. The demonstrated variability in left ventricular mass is important, yet frequently ignored. Recognizing left ventricular mass changes may facilitate the detection of myocardial injury reflected as edema.

Animals↗
PubMed1984

Heart-rate effects on canine left-ventricular end-diastolic compliance measured by two-dimensional ultrasound.

Despite recent interest in left ventricular (LV) compliance during open-heart surgery, the effect of heart rate (HR) remains unclear due to technical limitations of previous studies. In the presence of Formalin-induced complete atrioventricular (AV) block, AV sequentially paced heart rate was varied between 100, 125, and 150 beats/min in eight dogs on cardiopulmonary bypass. The heart was cradled in an open pericardial well filled with ultrasound-conducting gel. LV end-diastolic pressure (LVEDP) was varied over 0-20 mm Hg by flow regulation in the bypass circuit. Left ventricular end-diastolic volume (LVEDV) was calculated from three orthogonal two-dimensional (2-D) echocardiographic sections using Simpson's rule. Exponential curves derived from the relation LVEDP = ke(bxLVEDV) demonstrated a small, but significant increase in the mean exponential constants (b = 0.034, 0.037, and 0.049 at HR 100, 125, and 150, respectively) reflecting progressive stiffening with increasing heart rate. However, mean overall pressure-volume relations were not significantly altered when analyzed in four separate intervals of LVEDP. It is concluded that although LV volume determinations with 2-D echocardiography demonstrate a steady trend toward decreased end-diastolic LV compliance with increasing rate, this change is so small as to make heart rate a minor determinant of observed intraoperative compliance changes.

Animals↗