Biomedical subjects

Henry M Spotnitz

Publications and source records attributed to Henry M Spotnitz.

26 records · Page 2Linked to original sources

PubMed2003

Correlation of the Tei index with invasive measurements of ventricular function in a porcine model.

BACKGROUND: The Doppler myocardial performance (Tei) index has been reported to be clinically useful in assessing left ventricular systolic and diastolic function in both adults and children. However, there are limited data to compare the Tei index with invasive measurements of ventricular function. We used a porcine model to directly correlate the Tei index with invasive indices of systolic and diastolic function. METHODS: Pressure volume loops were obtained from 10 pigs (32-45 kg). A micromanometer and a conductance catheter were placed in the left ventricle to record pressure and volume, respectively. A flow probe was placed around the ascending aorta to record cardiac output. Baseline pressure volume loops were generated during preload reduction through caval occlusion. Epicardial echocardiograms were performed just before the caval occlusion. Invasive indices including preload recruitable stroke work, ventricular stiffness constant, and cardiac output were assessed, as were noninvasive echocardiographic indices including Tei index and ejection fraction. An ischemic insult, ventricular fibrillation, was induced to alter ventricular function. After cardioversion and 40 minutes of reperfusion, echocardiographic and invasive measurements were repeated. RESULTS: There was a statistically significant inverse relationship between the percent change in Tei and the percent change in preload recruitable stroke work after ventricular fibrillation (r = -0.70, P =.02), although the correlation between the actual values of Tei and preload recruitable stroke work were not statistically significant. There was a statistically significant inverse relationship between the percent change in Tei and the percent change in cardiac output (r = -0.65, P =.03). There was a direct correlation between the value of Tei and the ventricular stiffness constant at baseline (r = 0.63, P <.05). As anticipated, the value of Tei was inversely related to ejection fraction by epicardial echocardiogram at baseline (r = -0.85, P <.001). The percent change in Tei was inversely related to the percent change in ejection fraction as well (r = -0.69, P <.05). CONCLUSIONS: This animal model is one of the first studies to demonstrate a direct correlation between the Tei index and systolic and diastolic invasive measurements of ventricular function. This supports the clinical use of this index as a measure of global ventricular function.

Animals↗

PubMed2003

Aortic regurgitation in the heterotopic rat heart transplant: effect on ventricular remodeling and diastolic function.

OBJECTIVES: Use of the heterotopic rat cardiac isograft model is limited by ventricular atrophy attributable to the left ventricle's non-working state. Previous studies indicate that increased left ventricular pressure-volume work minimizes atrophy. We used a simpler approach to increase ventricular work, imposing aortic regurgitation on the transplant. We hypothesized that this would prevent atrophy and preserve left ventricular compliance. METHODS: We analyzed heterotopic transplants with aortic valvotomy and without aortic valvotomy (controls). Recipient native hearts served as separate controls. After 15 to 25 days, we measured cardiac wet weight, dry weight, and water content of all groups and measured echocardiographic left ventricular wall thickness and end-diastolic and end-systolic diameters in both transplant groups. Left ventricular volume infusions yielded pressure-volume data that we analyzed using regression methods. RESULTS: Aortic regurgitant transplants weighed more than control transplants (dry weight, 0.109 +/- 0.013 g vs 0.097 +/- 0.016 g; p = 0.020, 2-way analysis of variance), but all transplants weighed less than native hearts weighed (p = 0.001). Control transplants were less compliant than regurgitant transplants (p = 0.002), but the latter were similar to their own native hearts (p = 0.34). Wall thickness decreased in regurgitant vs control transplants (p = 0.020, Student's t-test), but end-diastolic and end-systolic diameters increased (p < or = 0.001). CONCLUSIONS: Aortic regurgitation in heterotopic transplants improves left ventricular compliance through chamber dilatation without preventing atrophy. Moderate acute aortic regurgitation affects ventricular remodeling more than it stimulates myocardial hypertrophy. Smaller end-diastolic diameter, greater wall thickness, and myocardial edema may explain decreased compliance in non-working transplants.

Animals↗

PubMed2003

Optimizing probucol administration to preserve left ventricular compliance after reperfusion injury in the heterotopic rat heart isograft.

BACKGROUND: We investigated the optimal method of administering probucol to attenuate reperfusion-induced diastolic abnormalities in the left ventricle of the heterotopically transplanted rat heart isograft. METHODS: We assigned Lewis rats (n = 84) to 7 transplant groups. We arrested 42 hearts using coronary perfusion with hypothermic University of Wisconsin (UW) solution at 60 mm Hg and abdominally isografted the hearts. Neither donors nor recipients in the control group (C-C, n = 6) received probucol. Oral probucol (1% by weight in chow) was fed for 1 month before surgery to the donors only (OP-C, n = 6), the recipients only (C-OP, n = 6), or both (OP-OP, n = 6). We administered an intraperitoneal injection of probucol (300 mg/kg) in 3 ml oil 1 hour before surgery to the donors only (IP-C, n = 6), the recipients only (C-IP, n = 6), or both (IP-IP, n = 6). Transplanted hearts were reperfused for 15 minutes and re-arrested. We also arrested the control recipients' native hearts (native, n = 6). We measured post-mortem left ventricular compliance curves and myocardial water content. RESULTS: The most compliant grafts were in Groups IP-IP, OP-OP, and C-IP. All isograft groups had significantly less left ventricular compliance than did native hearts. Myocardial water content was significantly greater in controls than in natives, OP-OP, and OP-C. CONCLUSIONS: Pre-treatment with intraperitoneal probucol in cardiac isograft recipients combines optimal protection with simple administration when UW solution is used for both arrest and preservation. Further studies of the protective effect of probucol against reperfusion injury in large-animal models are warranted and should use intraperitoneal or intravenous injection in recipients.

Administration, Oral↗

PubMed2002

Regional variation in myocardial water content in the edematous pig heart.

BACKGROUND: The purpose of this study was to examine regional variation in myocardial water content (%MWC) throughout the iatrogenically edematous pig heart. METHODS: Edema was induced by hemodilution in domestic swine (n = 26). Hearts were arrested with potassium chloride. The left ventricular free wall (LVFW), interventricular septum (IVS), and right ventricular free wall (RVFW) were biopsied at the apex, base, and equator. Full-thickness biopsy (Full, 0.5-1 g) and subendocardial (Endo, 0.1-0.2 g) biopsies were removed from each region. %MWC was determined for each biopsy. RESULTS: The %MWC for all hearts were as follows: Endo, 81.1 +/- 0.1, and Full, 80.6 +/- 0.1* (*P < 0.02); apex, 81.1 +/- 0.2*, equator, 80.7 +/- 0.2, and base, 80.4 +/- 0.2 (*P < 0.02); RVFW, 81.4 +/- 0.3*, IVS, 80.8 +/- 0.2*, and LVFW, 80.3 +/- 0.1* (*P < 0.02). For 18 hearts with LV samples with average %MWC >or= 80%, the percentages were apex, 81.4 +/- 0.2*, equator, 81.0 +/- 0.2*, and base, 80.6 +/- 0.2* (*P < 0.02) (repeated measures, ANOVA). CONCLUSION: In the iatrogenically edematous porcine heart, a significant water gradient exists, with Endo > Full, apex > equator > base, and RVFW > IVS > LVFW. These results indicate that when examining edema, consistent biopsy results depend on a reproducible sampling site. Water content tends to be highest in thin-walled portions of the heart, suggesting that contractile force may be important in the distribution of edema.

Animals↗

PubMed2002

Left ventricular end-diastolic volume from ejection fraction and stroke volume in pigs during IVC occlusion.

BACKGROUND: Real-time measurement of left ventricular end-diastolic volume (LVEDV), combined with left ventricular end-diastolic pressure (LVEDP), would allow continuous measurement of intraoperative diastolic function. In pursuit of this goal, we examined stroke volume divided by ejection fraction for calculation of LVEDV(sv/ef). METHODS: Five anesthetized pigs underwent median sternotomy and pericardiotomy. A transit-time ultrasonic flow probe on the ascending aorta provided cardiac output. A micromanometer provided LV end-diastolic pressure. End-diastolic and end-systolic areas were measured from LV short-axis cross sections to obtain ejection fraction. LVEDV(sv/ef) was calculated during IVC occlusion. Steady-state LVEDV(echo) was determined using a three-plane echocardiography model. LVEDV(echo) was used to validate steady-state LVEDA in each experiment. RESULTS: Correlation coefficients for linear and pressure-volume relation analyses ranged from 0.46 to 0.99. The two methods for measuring LVEDV generated compliance curves with an overall reliability coefficient of 0.84. CONCLUSIONS: The LVEDV(sv/ef) method may facilitate real-time determination of LV compliance.

Animals↗

PubMed2002

Transesophageal echocardiography guided placement of a coronary sinus pacing lead.

Cardiac resynchronization therapy for the treatment of medically refractory heart failure requires coronary sinus lead placement for left ventricular pacing. Coronary sinus lead placement is technically difficult with success rates reported between 53% to 98% and implantation times ranging from 90 minutes to 5 hours. We report the use of intraoperative transesophageal echocardiography to guide coronary sinus lead placement when conventional fluoroscopy failed. Transesophageal echocardiography may improve the success rate with coronary sinus lead placement and decrease the operative time required. This should be used with caution, however, as sedation, possible intubation, and esophageal manipulation have potentially morbid consequences in patients with advanced congestive heart failure.

Aged↗

PubMedDate not supplied

Validation study of PulseCO system for continuous cardiac output measurement.

Ultrasonic flow probes have been used to optimize biventricular pacing immediately after cardiopulmonary bypass, improving cardiac output (CO) by 10%; however, flow probes must be removed with chest closure. The PulseCO system (LiDCO Limited, Cambridge, UK) may extend optimization into the postoperative period, but controlled validations have not been reported. Six anesthetized pigs were instrumented for right heart bypass. Flow was varied from 3 to 1 L/min and then back to 3 in 0.5 L/min increments for 60 second intervals. CO was measured by ultrasonic flow probe on the aorta and by PulseCO using a femoral arterial line. PulseCO and flow probe accurately measured CO (PulseCO R2: 0.79-0.95; flow probe R2: 0.96-0.99). At flow of 2 L/min, when the heart was paced 30 bpm over the sinus rate, PulseCO falsely indicated an increase in CO (2.13 vs. 2.30 L/min, p = 0.014). When mean arterial pressure was increased by 20% using a phenylephrine infusion, PulseCO falsely indicated an increase in CO (2.13 vs. 2.47 L/min, p = 0.014). When mean arterial pressure was decreased by 20% using a nitroprusside infusion, PulseCO falsely indicated a decrease in CO (2.13 vs. 1.79 L/min, p = 0.003). PulseCO appears to be useful for assessing acute changes in CO if its limitations are recognized.

Animals↗

PubMedDate not supplied

Validation of mean arterial pressure as an indicator of acute changes in cardiac output.

Changes in mean arterial pressure (MAP) are often assumed to reflect changes in cardiac output (CO). A linear relationship is postulated to exist between these two quantities based upon the circuit model for systemic circulation. Previous studies have correlated changes in CO and MAP. However, to our knowledge, no studies have tested the relationship between CO and MAP in vivo without changes in systemic vascular resistance. Research on baroreceptor stimulation and vasomotor response has shown that vasomotor tone changes 15 to 60 seconds after an acute change in CO. Maximal activation of vasomotor response occurs after approximately 30 seconds. Thus MAP should correlate directly with CO during acute changes (< 15 seconds). To test this, we examined the relationship between CO and MAP during 10 second occlusions of the inferior vena cava in anesthetized pigs. A linear relationship existed between CO and MAP in seven pigs (%MAP = 0.60[%CO] - 0.41, p = 0.0001). This study validates the use of MAP as an indicator of acute changes in CO. Fluctuations in MAP correlate well with acute changes in CO in the absence of changes in vascular tone.

Animals↗