Biomedical subjects

M M Amirhamzeh

Publications and source records attributed to M M Amirhamzeh.

16 recordsLinked to original sources

PubMed1999

Pressure volume curves in arrested heterotopic rat heart isografts: role of improved myocardial protection.

BACKGROUND: To minimize decreases in left ventricular (LV) compliance immediately after rat heart transplantation, we tested several different methods of myocardial protection. MATERIALS AND METHODS: Five groups of ACI rat hearts (n = 6 each) were arrested by coronary perfusion with 5 ml of UW (University of Wisconsin), UW-BDM (UW with 2,3-butanedione monoxime), CU (Columbia University), or CU-BDM solution or by LV injection of potassium chloride and Ringer's lactate immersion (KCl/RL). After abdominal isografting and blood reperfusion for 15 min, transplanted hearts (TxH) were arrested and excised. Diastolic LV pressure-volume curves (LVPVCs) were correlated with myocardial water content (MWC). Native hearts (NH) were arrested identically to TxH and maintained at 4 degrees C by immersion. LVPVCs were measured at 15-min intervals for 90 min. RESULTS: In three of four pressure intervals at Time 0, normalized LV volume (LVV) was smaller (P < 0.05, ANOVA) in KCl/RL native hearts than in the four perfusion groups. LVV decreased significantly in NH after 45-75 min; LVV decreased similarly with time in all groups. In TxH, postarrest LVVs were higher with UW-BDM, CU-BDM, and CU than with UW or KCl/RL (P < 0.05, ANOVA). Expressing LVV of TxH as a percentage of NH, UW-BDM, CU, and CU-BDM provided qualitatively better diastolic properties than KCl/RL and UW. CONCLUSIONS: Thus rat LVPVCs can be improved after heart transplantation with alternative strategies of myocardial protection. KCl arrest decreases LV filling volume in this model and should be avoided.

Abdomen↗

PubMed1999

Coronary perfusate composition influences diastolic properties, myocardial water content, and histologic characteristics of the rat left ventricle.

BACKGROUND: Recent studies found that edema, histology, and left ventricular diastolic compliance exhibit quantitative relationships in rats. Edema due to low osmolarity coronary perfusates increases myocardial water content and histologic edema score and decreases left ventricular filling. The present study examined effects of perfusate osmolarity and chemical composition on rat hearts. METHODS: Arrested American Cancer Institute (ACI) rat hearts (4 degrees C) were perfused with different cardioplegia solutions, including Plegisol (289 mOsm/L), dilute Plegisol (172 mOsm/L), Stanford solution (409 mOsm/L), and University of Wisconsin solution (315 mOsm/L). Controls had blood perfusion (310 mOsm/L). Postmortem left ventricular pressure-volume curves and myocardial water content were measured. After glutaraldehyde or formalin fixation, dehydration, and paraffin embedding, edema was graded subjectively. RESULTS: Myocardial water content reflected perfusate osmolarity, being lowest in Stanford and University of Wisconsin solutions (p<0.05 versus other groups) and highest in dilute Plegisol (p<0.05). Left ventricular filling volumes were smallest in dilute Plegisol and Plegisol (p<0.05). Osmolarity was not a major determinant of myocardial edema grade, which was highest with University of Wisconsin solution and dilute Plegisol (p<0.05 versus other groups). CONCLUSIONS: Perfusate osmolarity determined myocardial water content and left ventricular filling volume. However, perfusate chemical composition influenced the histologic appearance of edema. Pathologic grading of edema can be influenced by factors other than osmolarity alone.

Adenosine↗

PubMed1998

Reversal of iatrogenic myocardial edema and related abnormalities of diastolic properties in the pig left ventricle.

OBJECTIVE: This study examines the resolution of iatrogenic edema and related changes in systolic and diastolic properties in the intact pig left ventricle. METHODS: The coronary arteries were perfused for 50 to 60 seconds with diluted blood (hematocrit value 10% +/- 1%, edema group, n = 5) or whole blood (hematocrit value 28% +/- 1%, control group, n = 6) infused into the aortic root during aortic crossclamping in conditioned, anesthetized pigs. After whole blood reperfusion, preload reduction by vena caval occlusion was used to define systolic and diastolic properties at 15-minute intervals. Left ventricular pressure and conductance, aortic flow, and two-dimensional echocardiography were recorded. RESULTS: Left ventricular mass (wall volume) in the edema group increased significantly compared with that in control pigs after crossclamp removal. Mass returned to preperfusion levels after 45 minutes. The ventricular stiffness constant (beta) increased significantly in the edema group versus the control group, returning to baseline by 30 minutes. The diastolic relaxation constant (tau) and base constant (alpha) did not differ between groups. There was no significant change in contractility. CONCLUSION: Increases in left ventricular mass and diastolic stiffness induced by coronary perfusion with hemodiluted blood resolve after 45 minutes of whole blood perfusion in pigs. This study defines physiologic effects of edema in the normal heart while eliminating most common confounding experimental errors.

Animals↗

PubMed1998

A method for detecting changes in left ventricular mass during variations in filling volume.

Two-dimensional echocardiography has been useful for measuring changes in left ventricular mass (LVM) at constant left ventricular end-diastolic volume (LVEDV). Two-dimensional echocardiographic measurement of LVM changes during variations in LVEDV requires definition of the LVM/LVEDV relation because two-dimensional echocardiographic measurements could be affected by asymmetrical redistribution of LVM. Echocardiography data were recorded during caval occlusions in pigs (n = 6). Results confirm that A(M) (left ventricular [LV] short-axis cross-sectional [SACS] wall thickness area), was inversely related to AL (LV SACS lumen area), the average relation being A(M) = -0.33 AL + 20 (r = 0.82 +/- 0.05 [SE]). In addition, we developed a model that computes normal relation between LV SACS wall thickness area (AMc) and LV SACS lumen area (ALc) over a physiologic range of LVEDVs based on a single end-diastolic two-dimensional echocardiographic SACS image. Each computed relation corresponds uniquely to an LVM (LVMc). Theoretically, a difference between AMc/ALc relation before an intervention and the computed relation after the intervention would indicate a change in LVM. To test the utility of this model, edema was induced in a second group of pigs (n = 6) by coronary hemodilution. Two conditions were tested: pre-edema and edema. Serial AMc/ALc and LVMc were computed. Pre-edema and edema AMc were compared at matched LV SACS end-diastolic areas (ALc = 15 cm2). Results showed a significant increase in LVMc (two-tailed p value < 0.05), as observed by two-dimensional echocardiography. We conclude that the A(M) and AL are inversely related. This relation is useful for detecting alterations in LVM during variations in LVEDV.

Animals↗

PubMed1998

Effect of improved myocardial protection on edema and diastolic properties of the rat left ventricle during acute allograft rejection.

BACKGROUND: Studies of myocardial edema and diastolic dysfunction in rat heart transplantation have been flawed by ischemic injury. This study uses improved methods to prevent ischemic contracture. METHODS: Hearts of 30 ACI rats were transplanted into the abdomen of Lewis rats by use of cold University of Wisconsin solution for improved preservation. Left ventricular diastolic properties were expressed as volume at standardized pressure intervals. RESULTS: On posttransplantation day 3, mean left ventricular volume at 15 mm Hg in allografts (290 +/- 9 microl, SEM) was not significantly different vs isografts (299 +/- 32 microl), allografts on day 0 (337 +/- 28 ml) or day 1 (324 +/- 20 microl), or native hearts (334 +/- 19 microl). However, volume was reduced to 173 +/- 17 microl on day 4 and to 70 +/- 23 microl on day 5 (p < 0.05). Similar findings were obtained for volume at 5 and 10 mm Hg. Allograft myocardial water content on day 3, 76.3% +/- 5%, similar to allografts on day 0 and 1 and to isografts on day 3, increased to 77.6% +/- 8% on day 4 (NS) and 79.4% +/- 6% on day 5 (p < 0.05 vs day 0). Histologically, rejection in allografts was mild on day 3, moderate on day 4, and severe on day 5. CONCLUSIONS: Reduced left ventricular filling volume during rejection is only partially explained by edema. Abnormalities of diastolic properties previously attributed to the unloaded state of nonworking heart models may actually reflect inadequate peritransplantation myocardial protection.

Adenosine↗

PubMed1997

Myocardial edema: comparison of effects on filling volume and stiffness of the left ventricle in rats and pigs.

BACKGROUND: This study compared the adverse effects of crystalloid-induced myocardial edema on left ventricular (LV) compliance in small and large hearts. METHODS: Plegisol (289 mOsm/L) was perfused into the coronary arteries of pigs (n = 8) and 1:1 dilute Plegisol (145 mOsm/L) into the coronary arteries of rats (n = 6). Pressure-volume relations, heart weight, and water content were then determined. The pressure-volume relations were compared using an LV volume at a pressure of 10 mm Hg. RESULTS: Edema in rats was associated with significant (p < 0.05) increases in heart weight (1.1 +/- 0.0 g versus 1.4 +/- 0.1 g [average +/- standard error of the mean]) and water content (76.8% +/- 0.4% versus 81.3% +/- 0.8%), but an increase in LV stiffness (7.91 +/- 0.52 versus 9.27 +/- 1.42) and a decrease in the LV volume at 10 mm Hg (0.25 +/- 0.02 mL versus 0.14 +/- 0.05 mL) were not statistically significant. Edema in pigs was associated with statistically significant (p < 0.05) increases in LV stiffness beta (0.050 +/- 0.004 versus 0.072 +/- 0.008), heart weight (207 +/- 8 g versus 274 +/- 9 g), and water content (79.8% +/- 0.6% versus 85.3% +/- 0.6%) and a significant decrease in the LV volume at 10 mm Hg (88.4 +/- 5.8 mL versus 60.4 +/- 6.8 mL). CONCLUSIONS: Myocardial edema is associated with an increase in water content and LV stiffness and a decrease in the LV volume at 10 mm Hg in both species. In rats, however, the water content is smaller in the control state and a more hypotonic perfusate is needed to induce a given degree of edema.

Animals↗

PubMed1997

A comparative study of treadmill tests and heel raising exercise for peripheral arterial disease.

OBJECTIVES: This two part study validated a 1 min treadmill exercise test and compared this with simple heel raising exercise. METHODS: In an initial study of 24 claudicants (aged 43-79, median 63 years), ankle pressures were measured immediately after repeated treadmill exercises: for 1 min, until onset of claudication, and until maximum tolerated walking distance. Absolute value, fall and percent change in pressures were calculated. The results of this part of the study were then used as a "gold standard" for comparison with 30 s of heel raising and treadmill exercise. This second stage was performed on 21 symptomatic limbs (14 claudicants aged 42-73, median 69 years). RESULTS: Variability was least for pressures expressed as percent change after 1 min of exercise. The paired t-test revealed a significant correlation between the two methods of exercise (p < 0.05). CONCLUSION: Heel raising produced changes in ankle pressure which correlated well with those induced by treadmill exercise. We recommend the use of simple heel raising when a stress test is required to diagnose lower limb arterial insufficiency in the outpatient clinic.

Aged↗

PubMed1996

Validation of right and left ventricular conductance and echocardiography for cardiac function studies.

BACKGROUND: Continuous estimation of left ventricular volume from instantaneous conductance has compared favorably with "gold standards," is less labor intensive, and provides real-time data. Little information exists, however, correlating right ventricular conductance with such gold standards or examining the effects of an electrical field generated in the opposite ventricle. METHODS: In open-chested sheep, right and left ventricular conductance, two-dimensional echocardiography, and thermodilution cardiac outputs were measured at steady-state conditions. After these measurements, postmortem pressure-volume relations, ventricular mass, and ventricular casting were performed. RESULTS: The corrected end-diastolic volume measured by conductance correlated well with volumes measured by echocardiography (r = 0.89), postmortem pressure-volume relations (r = 0.84), and casts (r = 0.85). Left ventricular end-diastolic volume measured by conductance did not differ significantly from other standards by analysis of variance. The presence of an electrical field in the opposite ventricle did not affect measured conductance in the studied ventricle. CONCLUSIONS: Conductance is useful for the measurement of right and left ventricular end-diastolic volumes in the beating heart and is not affected by the presence of an electrical field in the opposite ventricle. Hence, conductance is a useful tool in studies involving interventricular dependence and function.

Animals↗

PubMed1996

Iatrogenic myocardial edema: increased diastolic compliance and time course of resolution in vivo.

BACKGROUND: Perfusion-induced edema reduces diastolic compliance in isolated hearts, but this effect and the time for edema to resolve after blood reperfusion have not been defined in large animals. METHODS: Edema was induced by coronary perfusion with Plegisol (750 mL, 289 mOsm/L) during a 1-minute aortic occlusion in 6 pigs. This was followed by whole blood reperfusion, inotropic support, and circulatory assistance until sinus rhythm and contractile function were restored. A control group (n = 6) was treated similarly, with 1 minute of electrically induced ventricular fibrillation and no coronary perfusion. Recorded data included electrocardiogram, left ventricular pressure and conductance, aortic flow, and two-dimensional echocardiography. Preload reduction by vena caval occlusion was used to define systolic and diastolic properties. Data were recorded at baseline and at 15-minute intervals for 90 minutes after reperfusion. RESULTS: In the edema group, average left ventricular mass (132 +/- 7 [standard error of the mean] versus 106 +/- 4 g) and ventricular stiffness constant (0.15 +/- 0.02 versus 0.05 +/- 0.01) increased after Plegisol versus baseline (p < 0.05), returning to normal after 45 minutes of reperfusion. In controls, mass (118 +/- 6 versus 116 +/- 4 g) and ventricular stiffness (0.06 +/- 0.01 versus 0.05 +/- 0.01) did not change significantly. There was no significant change in systolic function. Myocardial water content at the end of the study was not different for the two groups. CONCLUSIONS: Crystalloid-induced edema and diastolic stiffness resolve after 45 minutes in pigs. This suggests that edema caused solely by cardioplegia during cardiac operations should not cause significant perioperative ventricular dysfunction.

Animals↗

PubMed1995

Discriminating between preservation and reperfusion injury in human cardiac allografts using heart weight and left ventricular mass.

BACKGROUND: Myocardial edema caused by injury during preservation or reperfusion can affect cardiac function after heart transplantation. This study was designed to distinguish these forms of injury in human allografts. METHODS AND RESULTS: In 15 donor hearts preserved in University of Wisconsin solution, heart weight (HW) was obtained immediately after explantation and after transport before implantation. Left ventricular mass (LVM) was calculated separately in 18 patients with the use of epicardial two-dimensional echocardiograms obtained both before explantation from the donor and after transplantation and weaning from cardiopulmonary bypass. While changes in LVM could be due to preservation or reperfusion injury, changes in HW can only be due to edema occurring during transport. HW averaged 339 +/- 24 g (mean +/- SE) before and 340 +/- 24 g after transport (P = NS); however, LVM increased 14 g, from 164 +/- 8 to 178 +/- 11 g (P < .05, paired t test). LVM increased in 10 of 18 patients (56%). No correlation was demonstrated between duration of ischemia (mean, 172 +/- 13 minutes) and changes in HW or LVM. Two patients died as a result of primary graft failure. In the first, HW increased 54 g, 2 SD above the mean. In the second, LVM increased 66 g, 2 SD above the mean, but HW changed minimally. CONCLUSIONS: While current preservation methods result in minimal change in HW during transport, reperfusion injury frequently increases LVM. LVM determination by two-dimensional echocardiography may prove valuable in detecting allograft injury.

Diagnosis, Differential↗

PubMed1994

Time course of perfusion-induced myocardial edema resolution in rats.

Previous studies have demonstrated that crystalloid coronary perfusion can cause myocardial edema, but the time required for resolution of this edema has not been defined. Accordingly, studies were conducted in 30 rats. Myocardial edema was induced by coronary perfusion with 20 cc/kg of Plegisol (294 mOsm/liter) during aortic occlusion, which produced diastolic arrest. This was followed by whole blood reperfusion, which restored normal contractile function. Duration of reperfusion in minutes was zero (group 0, n = 6), one (group 1, n = 6), five (group 5, n = 6), or fifteen (group 15, n = 6). A control group (n = 6) was studied without edema or reperfusion. Data included heart weight and myocardial water content. Left ventricular pressure-volume curves were measured in groups 1, 5, and 15. Myocardial water content increased significantly from 75.7 +/- 0.5% (SD) in the control group to 79.7 +/- 1.1% (P < 0.05) in group 0 and then decreased significantly to 77.3 +/- 0.7, 75.2 +/- 1.4, and 75.3 +/- 1.6% in groups 1, 5, and 15, respectively. Water content in group 1 was also significantly greater than in groups 5 and 15. Heart weight changes were not statistically significant. Normalized pressure-volume relationships shifted rightward with increasing reperfusion time, but changes were not statistically significant. We conclude that edema induced by crystalloid coronary perfusion of the arrested heart resolves in the beating heart after less than 5 min of blood reperfusion.

Animals↗

PubMed1994

Systolic arterial pressure recovery after ventricular fibrillation in pigs.

Ventricular fibrillation (VF) is induced during implantable cardioverter defibrillator insertion and can result in cardiovascular collapse. The relation between repeated VF trials of varying duration and systolic blood pressure (SBP) recovery rate was studied in 6 pigs. Two implantable cardioverter defibrillator patches were placed on the heart, and VF was varied in a cyclic pattern until cardiovascular collapse occurred. A negative logarithmic relation between SBP recovery rate and duration of VF was found in 4 of the pigs with correlation coefficients of 0.62 to 0.97 (p < 0.05). The overall correlation coefficient was 0.51 for all 116 data points (p < 0.001). Although there was a significant (p < 0.05) decrease in average (+/- standard error of the mean) baseline SBP in the second half of each experiment (83 +/- 5 mm Hg versus 77 +/- 6 mm Hg), no significant difference in SBP was observed during VF (17 +/- 1 mm Hg versus 16 +/- 1 mm Hg) or after 15 seconds of SBP recovery (51 +/- 4 mm Hg versus 46 +/- 3 mm Hg) between the two halves of the experiments. Cardiovascular collapse occurred without warning; epinephrine was effective in reversing it. In conclusion, SBP recovery rate and duration of VF have a negative logarithmic relation consistent with a negative effect on left ventricular contractility with prolongation of VF. The onset of cardiovascular collapse during implantable cardioverter defibrillator testing cannot be predicted on the basis of monitored blood pressure alone.

Animals↗

PubMed1994

Systolic arterial pressure recovery after ventricular fibrillation/flutter in humans.

Although the elective induction of cardiac arrest for implantable defibrillator insertion under general anesthesia is widely used, the hemodynamics of recovery of arterial blood pressure after cardiac arrest is not well-defined. Accordingly, the time course of recovery of systolic arterial pressure was studied in seven patients during the repetitive induction of ventricular fibrillation (n = 6) or ventricular flutter (n = 1). The mean number of episodes of cardiac arrest was 7 +/- 2, and the mean drop in systolic pressure was 84 +/- 16 mmHg. The mean recovery time for systolic pressure was 10 +/- 6 seconds, the average systolic pressure recovery rate was 13 +/- 14 mmHg/sec, and the mean percent systolic pressure recovery was 94% +/- 9%. A negative logarithmic relation was found to exist between the rate of systolic arterial pressure recovery and the duration of ventricular fibrillation or flutter with a correlation coefficient of 0.68 to 0.97 (P < 0.05) in five of the seven patients. A linear relation between the time for systolic pressure recovery and duration of asystole was also defined. These results are consistent with the view that prolongation of ventricular fibrillation or flutter increases the duration of arterial pressure recovery through a negative effect on left ventricular contractility. Increased understanding of these relations may lead to increased safety of implantable defibrillator insertion.

Adult↗

PubMed1994

Extrinsic factors influencing left ventricular conductance in situ.

BACKGROUND: The accuracy of conductance measurement of left ventricular (LV) volume is affected by parallel conductance (Vp) from right ventricular (RV) volume as well as surroundings of the heart. No studies have quantified the extrinsic influences on Vp. METHODS AND RESULTS: In six anesthetized pigs, using a median sternotomy and pericardial well, implantable cardioverter defibrillator patches, normal saline, or echocardiography gel were introduced and removed. LV end-diastolic pressure (LVEDP) did not change significantly with these interventions. Raw LV conductance was used to estimate end-diastolic volume (LVEDV), end-systolic volume (LVESV), and stroke volume (SV). Saline significantly increased mean +/- SEM calculated LVEDV from 106 +/- 8 to 131 +/- 6 mL and calculated LVESV from 81 +/- 7 to 110 +/- 5 mL; calculated SV decreased from 25 +/- 3 to 21 +/- 2 mL (P < .05, paired t test). Implantable cardioverter defibrillator patches and gel did not significantly change calculated LV volumes. LV conductance was also measured in arrested hearts during LV filling (5 to 60 mL) at four levels of RV volume (RVV). Using a fixed value for Vp, calculated mean LV volume was 30 +/- 3 mL at RVV = 0, 32 +/- 3 mL at RVV = 20, 33 +/- 3 mL at RVV = 40, and 36 +/- 3 mL at RVV = 60 (P < .01, repeated-measures ANOVA). CONCLUSIONS: While implantable cardioverter defibrillator patches and gel have no statistically significant effect, saline and RVV affect LV volume calculations by conductance, requiring special techniques during cardiopulmonary bypass or caval occlusion.

Animals↗

PubMed1994

Diastolic function in the heterotopic rat heart transplant model. Effects of edema, ischemia, and rejection.

Decreased systolic ventricular function and compliance and increased left ventricular edema and mass have been demonstrated in cardiac allograft rejection. Whether decreased left ventricular compliance in rejection is caused by myocardial edema has not been examined, and compliance in the Ono-Lindsey model has not been reported. Heterotopic rat abdominal cardiac transplantation was performed in ACI isografts (n = 24) and in ACI to Lewis allografts (n = 24). Subgroups were studied on posttransplantation days 0, 1, 3, and 5 (each n = 6). Both transplanted hearts and native hearts were arrested with potassium for the assessment of myocardial water content, heart weight, and the left ventricular pressure-volume relation. In transplanted hearts, myocardial water content did not change in isografts but increased on posttransplantation day 5 in allografts (81.1% on posttransplantation day 5 versus 76.1% on day 0, 77.2% on day 1, and 77.5% on day 3, p < 0.05). Wet and dry heart weight also increased on posttransplantation day 5 in allografts (p < 0.05). The left ventricular pressure-volume relation in transplanted hearts shifted to the left when compared with that in native hearts in all subgroups; these volume differences were statistically significant (p < 0.01) for all pressures above 7.5 mm Hg. This pattern was similar in isografts and allografts on posttransplantation days 0, 1, and 3, and no significant differences between isografts and allografts were demonstrated. On posttransplantation day 5, however, the pressure after a 0.05 ml injection in allografts was greater in transplanted hearts than in native hearts (24 +/- 3 versus 3 +/- 1 mm Hg, p < 0.01). The pressure difference between transplanted and native hearts was also significantly greater in allografts than in isografts (22 +/- 2 versus 6 +/- 1 mm Hg, p < 0.01), indicating an increase in stiffness of allografts. Thus edema and impaired diastolic properties occur concurrently with allograft rejection. Left ventricular volume is abnormal from posttransplantation days 0 to 5 in transplanted hearts but not native hearts in the Ono-Lindsey model with current methods, apparently because of ischemic injury during transplantation.

Animals↗

PubMedDate not supplied

Conductance-echocardiography correlation during changes in left ventricular volume.

Conductance (COND) measurements of left ventricular volume, satisfactory under steady state conditions, may be altered by extraneous factors during complex experiments or cardiac surgery. A reference technique is needed to detect changes in the COND-left ventricular volume relationship. This technique should indicate when recalibration of COND is needed. Accordingly, we assessed the relationship between left ventricular COND and the area of left ventricular short-axis cross section (SACS) by two-dimensional echocardiography during vena caval occlusion. Thirteen anesthetized pigs underwent a median sternotomy and insertion of a COND catheter. Two-dimensional echocardiography and COND were displayed and recorded simultaneously on a digital video monitor. Data were analyzed at end-diastole during the filling phase after vena caval occlusion, because the quality of two-dimensional echocardiography was better during recovery. Results demonstrated a linear relationship between left ventricular COND and SACS at end-diastole, with a positive slope. Correlation coefficients ranged from 0.88 to 1.0 and averaged 0.96 +/- 0.01 (SE). The overall mean relationship was (SACS) = 0.40 (COND) - 17. It is concluded that SACS by two-dimensional echocardiography can be employed to confirm COND measurements of left ventricular end-diastolic volume during laboratory experiments or cardiac surgery. Stability of the SACS-COND relationship indicates that COND calibration is valid. Changes in the SACS-COND relationship would require recalibration of COND. Data markedly deviating from a linear SACS-COND relation reflect experimental error and should be discarded.

Animals↗