Experimental cardiomyopathy as a model of chronic heart failure

Chronic Heart Failure Model Induced by Coronary Embolization in Sheep

Objective

To create a model of chronic heart failure in a large animal.

Methods

Heart failure was induced in sheep by single intracoronary injection of polymer macrobeads, which were administered into left main coronary artery (n=3) or selectively into left anterior descending (n=4) or left circumflex (n=5) coronary artery. The animals were followed by echocardigraphy for 20 weeks. Measurements comprised fractional area change (FAC), and diastolic ventricular area (EDVA) and regional wall-thickening fraction (WT%).

Results

EDVA increased from 14.2±2.1 cm2 prior to embolization to 16.9±3.1 cm2 on day 1 (p<0.05), and remained significantly increased until completion of the follow-up period. FAC dropped from 47.9±4.6% at baseline to 29.3±4.4% on day 1 (p<0.001) and remained significantly depressed until 20 weeks later. In 9 selectively embolized animals WT% of the embolized area decreased from 33.8±8.0% at baseline to 5.3±2.6% on day 1 and remained significantly decreased.

Conclusions

A simple model of chronic heart failure was developed. It shows relatively high stability over time and may prove beneficial in experimental work on ventricular assist devices.

Assessment of cardiac troponin I (cTnI) and tissue velocity imaging (TVI) in 14 dogs with malignant lymphoma undergoing chemotherapy treatment with doxorubicin

Doxorubicin has been shown to be cardiotoxic at high doses but is an efficacious chemotherapeutic agent in the treatment of canine lymphoma. Echocardiographic measurements and serum ultrasensitive cardiac troponin I (cTnI) levels were obtained before and after doxorubicin administration in 14 dogs diagnosed with lymphoma. The aim of this prospective study was to evaluate changes in cTnI concentrations and tissue velocity imaging (TVI) values in dogs with lymphoma undergoing chemotherapy with doxorubicin. A total of 182 cTnI and 1017 TVI measurements were performed. Standard echocardiographic parameters, tissue Doppler indices and cTnI concentrations did not differ at any time point within a 12-week cyclic combination protocol. In conclusion, the use of doxorubicin at standard doses in the treatment of canine lymphoma may not be associated with significant myocardial damage.

Bovine model of doxorubicin-induced cardiomyopathy

Left ventricular assist devices (LVADs) constitute a recent advance in heart failure (HF) therapeutics. As the rigorous experimental assessment of LVADs in HF requires large animal models, our objective was to develop a bovine model of cardiomyopathy. Male calves (n = 8) were used. Four animals received 1.2 mg/kg intravenous doxorubicin weekly for seven weeks and four separate animals were studied as controls. Doxorubicin-treated animals were followed with weekly echocardiography. Target LV dysfunction was defined as an ejection fraction ≤35%. Sixty days after initiating doxorubicin, a terminal study was performed to determine hemodynamic, histological, biochemical, and molecular parameters. All four doxorubicin-treated animals exhibited significant (P < 0.05) contractile dysfunction, with target LV dysfunction achieved in three animals. Doxorubicin-treated hearts exhibited significantly reduced coronary blood flow and interstitial fibrosis and significantly increased apoptosis and myocyte size. Gene expression of atrial natriuretic factor increased more than 3-fold. Plasma norepinephrine and epinephrine levels were significantly increased early and late during the development of cardiomyopathy, respectively. We conclude that sequential administration of intravenous doxorubicin in calves induces a cardiomyopathy with many phenotypic hallmarks of the failing human heart. This clinically-relevant model may be useful for testing pathophysiologic responses to LVADs in the context of HF.

An ovine model of chronic heart failure: echocardiographic and tissue Doppler imaging characterization

BACKGROUND AND AIM OF THE STUDY

Heart failure in the western world is a major health-care issue. In order to validate novel surgical or pharmacological treatments, reproducible animal models of left ventricular dysfunction are necessary. In the current study, we report our data and experience with a model of toxin-induced heart failure in the sheep.

METHODS

Sequential intracoronary injections of doxorubicin (0.75 mg/kg) were carried out every 2 weeks until standard echocardiographic and tissue Doppler imaging detection of myocardial systolic dysfunction. The animals were assessed 1 month later and harvested. Indices of cardiac function from baseline to last day of protocol were recorded and their differences were evaluated by a Wilcoxon rank test for paired data.

RESULTS

Ten sheep received 2.5 +/- 0.7 intracoronary injections of a cumulative dose of 88.8 +/- 25 mg/m2 doxorubicin. All available parameters demonstrated signs of severe cardiac dysfunction with statistical significance. All hearts demonstrated severe histological lesions, some of which were consistent with doxorubicin-induced toxicity.

CONCLUSIONS

The present study shows that this ovine model is reproducible and stable. It can therefore be relevant to the study of chronic heart failure. It will be incorporated in our future studies concerning novel treatments (such as cell therapy) of nonischemic dilated cardiomyopathy.

Telemetrically monitored arrhythmogenic effects of doxorubicin in a dog model of heart failure

A model of chronic heart failure has been induced in dogs by repeated intracoronary infusion of doxorubicin, which is an antineoplastic medication that has dose-limiting cardiotoxic side effects. Although many of the dogs receiving doxorubicin develop typical signs of dilated cardiomypathy over 4-6 weeks, some of them suddenly die before completing the four weekly infusions of the drug. The present study was undertaken to determine whether such sudden death may be caused by the development of fatal arrhythmias during doxorubicin treatment. This was assessed by telemetrically monitoring the EKG of seven dogs, which received intracoronary infusion of 1 mg/kg doxorubicin given in four divided weekly doses. The recordings were obtained for 8-10 h on alternate days up to 4 weeks. Echo-cardiographic recordings were obtained once a week. The acute effects with each infusion of doxorubicin included a significant increase in heart rate, and no significant change in QRS complex. The cumulative prolonged effects of doxorubicin included slight reduction in QRS amplitude and duration, and marked arrhythmic changes. Four out of seven dogs showed a spectrum of arrhythmic events such as single or groups of premature ventricular complexes (PVCs), bigeminy, ventricular tachycardia (VTAC), ventricular fibrillations (VFIB), and asystole. All dogs did not show each of the events listed above and the same dog did not show all the events all the time. One of these four dogs developed VFIB for 25 min and then asystole leading to sudden death. These studies conclusively showed that fatal arrhythmias develop in some of the dogs receiving doxorubicin treatment accounting for the sporadic incidence of sudden death. Prophylactic treatment with antiarrhythmic agents may prevent such adverse events.

Evaluation of cardiac troponin I and T levels as markers of myocardial damage in doxorubicin-induced cardiomyopathy rats, and their relationship with echocardiographic and histological findings

BACKGROUND

Cardiac troponins I (cTnI) and T (cTnT) have been shown to be highly sensitive and specific markers of myocardial cell injury. We investigated the diagnostic value of cTnI and cTnT for the diagnosis of myocardial damage in a rat model of doxorubicin (DOX)-induced cardiomyopathy, and we examined the relationship between serial cTnI and cTnT with the development of cardiac disorders monitored by echocardiography and histological examinations in this model.

METHODS

Thirty-five Wistar rats were given 1.5 mg/kg DOX, i.v., weekly for up to 8 weeks for a total cumulative dose of 12 mg/kg BW. Ten rats received saline as a control group. cTnI was measured with Access(R) (ng/ml) and a research immunoassay (pg/ml), and compared with cTnT, CK-MB mass and CK. By using transthoracic echocardiography, anterior and posterior wall thickness, LV diameters and LV fractional shortening (FS) were measured in all rats before DOX or saline, and at weeks 6 and 9 after treatment in all surviving rats. Histology was performed in DOX-rats at 6 and 9 weeks after the last DOX dose and in all controls.

RESULTS

Eighteen of the DOX rats died prematurely of general toxicity during the 9-week period. End-diastolic (ED) and end-systolic (ES) LV diameters/BW significantly increased, whereas LV FS was decreased after 9 weeks in the DOX group (p<0.001). These parameters remained unchanged in controls. Histological evaluation of hearts from all rats given DOX revealed significant slight degrees of perivascular and interstitial fibrosis. In 7 of the 18 rats, degeneration and myocyte vacuolisation were found. Only five of the controls exhibited evidence of very slight perivascular fibrosis. A significant rise in cTnT was found in DOX rats after cumulative doses of 7.5 and 12 mg/kg in comparison with baseline (p<0.05). cTnT found in rats after 12 mg/kg were significantly greater than that found after 7.5 mg/kg DOX. Maximal cTnI (pg/ml) and cTnT levels were significantly increased in DOX rats compared with controls (p=0.006, 0.007). cTnI (ng/ml), CK-MB mass and CK remained unchanged in DOX rats compared with controls. All markers remained stable in controls. Analysis of data revealed a significant correlation between maximal cTnT and ED and ES LV diameters/BW (r=0.81 and 0.65; p<0.0001). A significant relationship was observed between maximal cTnT and the extent of myocardial morphological changes, and between LV diameters/BW and histological findings.

CONCLUSIONS

Among markers of ischemic injury after DOX in rats, cTnT showed the greatest ability to detect myocardial damage assessed by echocardiographic detection and histological changes. Although there was a discrepancy between the amount of cTnI and cTnT after DOX, probably due to heterogeneity in cross-reactivities of mAbs to various cTnI and cTnT forms, it is likely that cTnT in rats after DOX indicates cell damage determined by the magnitude of injury induced and that cTnT should be a useful marker for the prediction of experimentally induced cardiotoxicity and possibly for cardioprotective experiments.

Partial left ventriculectomy in modified adriamycin-induced cardiomyopathy in the dog

BACKGROUND

The purpose of this study was to evaluate modified adriamycin-induced cardiomyopathy in the dog for research on partial left ventriculectomy (PLV).

METHODS

An intracoronary catheter was introduced into the left main stem via the first marginal branch in a retrograde fashion in 12 adult foxhound dogs. The catheter was connected to a percutaneous access port that was used for weekly adriamycin administration (10 mg over a 1-hour period on 5 occasions). Follow-up examinations (transthoracic echocardiography, hemodynamic parameters, cardiopulmonary status, neurohormones) were done before, 1 week after the last adriamycin administration, and then 6 weeks later. This protocol was performed in 6 dogs (control group: Group 1). The other 6 dogs underwent PLV 1 week after the last adriamycin administration (Group 2). After the last measurements, all dogs were killed with saturated potassium chloride under general anesthesia and the hearts were excised for histologic examination. All data were calculated as mean and standard error of the mean. Differences were calculated by the Wilcoxon signed-rank test for paired and unpaired data. p < 0.05 was considered statistically significant.

RESULTS

One dog from each group died suddenly during adriamycin administration (probably due to ventricular arrhythmia). In addition, 1 dog from Group 2 suffered from a severe systemic inflammatory response syndrome after PLV and died 36 hours after surgery. Thus, 5 dogs from Group 1 and 4 from Group 2 underwent the entire study protocol. Adriamycin administration resulted in a severe dilated cardiomyopathy that was comparable in both groups (significant increase of central venous pressure, mean pulmonary artery pressure, pulmonary wedge pressure, left ventricular end-systolic and end-diastolic diameters, oxygen extraction, troponin I and anti-diuretic hormone, whereas cardiac output, ejection fraction and venous oxygen saturation decreased significantly). Deterioration of cardiac function continued after termination of adriamycin administration in Group 1 dogs, albeit not as progressively as during adriamycin administration. In contrast, cardiac function improved in Group 2 dogs after PLV, but did not reach baseline values. Cardiac index increased and oxygen extraction (p = 0.03) decreased, resulting in an enhanced venous oxygen saturation (p = 0.02). In particular, the distance of the papillary muscles at end diastole (p = 0.02) and at end systole (p = 0.02) at the mid-papillary level decreased significantly after PLV, resulting in reduced left ventricular diameter and volume (statistically significant for left ventricular end-systolic diameter and volume). All hearts had severe histologic alterations characteristic of adriamycin-induced toxicity, including cytoplasmic vacuolation, myocyte degeneration and increased fibrosis.

CONCLUSION

Modified adriamycin-induced cardiomyopathy in the dog may be suitable for research on PLV.

Simultaneous angiotensin converting enzyme inhibition moderates ventricular dysfunction caused by doxorubicin

AIMS

The purpose of this study was to determine that the administration of an angiotensin converting enzyme (ACE) inhibitor enalapril would confer protection against doxorubicin-induced experimental heart failure, and attenuate the development of left ventricular dysfunction.

METHODS

Seventeen dogs were chronically instrumented with an intracoronary catheter and received doxorubicin weekly for 4 weeks. Animals were assigned to two groups: group 1: untreated heart failure; and group 2: simultaneous enalapril administration (5 mg twice a week). Hemodynamic data were obtained at week 0 and 12. Echocardiography was performed weekly.

RESULTS

Survival improved with simultaneous enalapril administration (36% in group 1 vs. 100% in group 2, P=0.04). The increase in the left ventricular end-diastolic pressure was significantly reduced at week 12 (17+/-1 mmHg in group 1 vs. 9+/-1 mmHg in group 2, P=0.0042). The fall in left ventricular stroke work index was significantly prevented (52% in group 1 vs. 21% in group 2, P=0.006). The increase in right ventricular end-diastolic diameter was significantly reduced by enalapril prophylaxis.

CONCLUSION

Simultaneous treatment with enalapril was beneficial in the prevention of doxorubicin-induced cardiomyopathy.

Adriamycin-induced cardiomyopathy in the dog--an appropriate model for research on partial left ventriculectomy?

OBJECTIVE

To evaluate the adriamycin-induced cardiomyopathy in the dog for research on partial left ventriculectomy (PLV).

METHODS

An intracoronary catheter was introduced into the left main stem via the first diagonal branch in a retrograde fashion in 6 adult FBI (Foxhound Boehringer Ingelheim) dogs weighing 30 to 35 kg. The catheter was connected to a percutaneous access port that was used for weekly adriamycin administration (10 mg over a 1-hour period for 5 times). Follow-up examinations (transthoracic echocardiography, hemodynamic parameters, cardiopulmonary status, and neurohormones) were done before, 1 week after the last adriamycin administration, and 6 weeks later. After the last measurements, all dogs were euthanized with saturated potassium chloride under general anesthesia and the hearts were excised for histologic examinations. All data were calculated as mean values and standard error of the mean. Differences were calculated by the Wilcoxon signed rank test for paired and unpaired data. p values less than 0.05 were considered significant.

RESULTS

Central venous pressure (2.2 +/- 0.8 vs 5.2 +/- 0.4 mm Hg, p = 0.03), mean pulmonary artery pressure (8.6 +/- 1.1 vs 12.4 +/- 0.5 mm Hg, p = 0.03), pulmonary wedge pressure (2.6 +/- 0.9 vs 7.0 +/- 0 mm Hg, p = 0.03), left ventricular endsystolic diameter (2.5 +/- 0.2 vs 3.1 +/- 0.4 cm, p = 0.03), and enddiastolic (4.5 +/- 0.2 vs 4.9 +/- 0.2 cm, p = 0.03) diameter increased significantly after adriamycin administration, whereas cardiac output (4.0 +/- 0.3 vs 3.3 +/- 0.1 liter/min, p = 0.03), stroke volume index (66.0 +/- 7.4 vs 54.0 +/- 3.9 ml/beat/m(2), p = 0.03), and ejection fraction (61.1 +/- 5.1 vs 37.7 +/- 5.7%, p = 0.03) decreased markedly. These changes were accompanied by a significant decline of oxygen delivery (1130 +/- 170 vs 790 +/- 65 ml/min, p = 0.03), which led to an enhanced oxygen extraction (0.12 +/- 0.01 vs 0.24 +/- 0.01, p = 0.03). Consequently, venous oxygen saturation (82.7 +/- 4.1 vs 71.3 +/- 2.5%, p = 0.03) decreased. Troponin I (0.02 +/- 0.025 vs 1.7 +/- 0.6 ng/ml, p = 0.03) and the anti-diuretic hormone (1.9 +/- 0.9 vs 20.0 +/- 1.9 pg/ml, p = 0.03) increased significantly after adriamycin administration. Deterioration of cardiac function continued after termination of adriamycin administration, albeit slower than during adriamycin administration. All hearts had severe histologic alterations, which were characteristic of adriamycin-induced toxicity: cytoplasmic vacuolation, myocyte degeneration, and increased fibrosis.

CONCLUSIONS

The adriamycin-induced cardiomyopathy in the dog is similar to the dilated cardiomyopathy in humans and may be an appropriate model for PLV.

Composite cardiac binding in experimental heart failure

BACKGROUND

Composite cardiac binding consists of wrapping the heart with a synthetic membrane and a pericardial interposition. The goal of the present study was to apply composite cardiac binding to a canine model of heart failure.

METHODS

Twenty dogs were randomized to 2 groups: untreated heart failure (group 1, n = 13) and heart failure pretreated by composite cardiac binding (group 2, n = 7). They received a total dose of 1 mg x kg(-1) of intracoronary doxorubicin over 4 weeks. Hemodynamic data were obtained at weeks 0, 7, and 12. All animals were followed up with weekly echocardiography for 12 weeks.

RESULTS

Survival in group 1 was 54% and in group 2 was 100% at week 12 (p = 0.0438). Left ventricular end-diastolic pressure increased by 153% in group 1 and by 59% in group 2 (p = 0.0395) at week 12. Ejection fraction decreased by 27% in group 1 and by 19% in group 2 (p = 0.4401) at week 12.

CONCLUSIONS

Composite cardiac binding significantly prolongs survival and attenuates left ventricular dilatation and the increase in left ventricular end-diastolic pressure associated to chronic heart failure. Further evaluation in established heart failure is needed. Composite cardiac binding may be used for the prevention of recurrent dilatation following reduction ventriculoplasty.

A canine model of heart failure by intracoronary adriamycin injection: hemodynamic and energetic results

BACKGROUND

To eliminate the noncardiac toxicities associated with Adriamycin (Pharmacia Upjohn, Kalamazoo, MI) and to avoid the need for surgical implantation of a coronary artery catheter, we proposed serial intracoronary infusions of Adriamycin (Pharmacia Upjohn) with a Judkins catheter to develop a nonsurgical but selective model of dilated cardiomyopathy in dogs.

METHODS AND RESULTS

Twenty-two dogs were entered onto the study. Each dog received four weekly injections of Adriamycin (Pharmacia Upjohn; 15 mg/wk) through a Judkins catheter and verapamil orally (5 mg/kg twice daily) for 4 weeks. Dogs were evaluated with echocardiography, right-sided cardiac catheterization, and endomyocardial biopsy at times 0 and 10 weeks. The left ventricular ejection fraction decreased from 0.65 +/- 0.04 to 0.48 +/- 0.11 (P = .0006). The left ventricular end-diastolic and end-systolic diameter indices increased from 42.00 +/- 2.17 to 46.92 +/- 5.81 mm (P = .0029) and from 27.65 +/- 2.59 to 35.00 +/- 6.84 mm, respectively (P = .0210). The mechanical cardiac efficiency decreased from 28.55% +/- 13.30% at baseline and 15.64% +/- 9.09% at 10 weeks (P = .001). Cardiac myocyte vacuolation was present on histological examination at 10 weeks. The mortality rate was 41%. Minimal systemic Adriamycin (Pharmacia Upjohn) toxicity was noticed.

CONCLUSION

Intracoronary injection of Adriamycin (Pharmacia Upjohn) in dogs induced a chronic dilated cardiomyopathy.

Myocardial oxygen consumption is affected by dynamic cardiomyoplasty in dogs with adriamycin-induced cardiomyopathy

The purpose of the study was to investigate a possible myocardial sparing effect by dynamic cardiomyoplasty. We directly measured cardiac work and myocardial oxygen consumption after dynamic cardiomyopathy in dogs with adriamycin-induced cardiomyopathy. Ten dogs with cardiomyopathy induced by 4 weekly intracoronary infusions of adriamycin were studied. Five dogs underwent right latissimus dorsi cardiomyoplasty with progressive myostimulation, and five served as controls. Right heart and coronary sinus catheterizations were performed at 0, 10, and 15 weeks. Four and two dogs, respectively, the cardiomyoplasty and the control group, survived until 15 weeks. Cardiac work was not different between the control and the cardiomyoplasty groups (p = 0.42). Myocardial oxygen consumption was less in the cardiomyoplasty group (185.70 +/- 37.22; 165.75 +/- 25.86; 161.40 +/- 54.14 J/min at 0, 10, and 15 weeks, respectively) compared to the control group (147.80 +/- 70.99; 275.00 +/- 103.24; 263.50 +/- 52.75 J/min at 0, 10, and 15 weeks, respectively, p = 0.019). Mechanical cardiac efficiency was not meaningfully different between the cardiomyoplasty group (16.08% +/- 5.39%; 20.51% +/- 5.89%; 20.67% +/- 11.98% at 0, 10, and 15 weeks, respectively) compared to the control group (15.29% +/- 8.06%; 9.40% +/- 1.22%; 13.40% +/- 2.29% at 0, 10, and 15 weeks, respectively, p = 0.093). Acute changes of the cardiosynchronization ratio (2:1, 1:1, OFF) did not affect myocardial oxygen consumption or cardiac work within the cardiomyoplasty group. Dynamic cardiomyoplasty reduced myocardial oxygen consumption in dogs with adriamycin-induced cardiomyopathy.