Doxorubicin-induced Changes of Ventricular Repolarization Heterogeneity: Results of a Chronic Rat Study

Activation recovery interval as an electrocardiographic repolarization index to detect doxorubicin-induced cardiotoxicity

BACKGROUND

It has been reported that early detection and treatment of cancer therapy- related cardiac dysfunction (CTRCD) improves its prognosis. The detailed relationships between electrocardiographic repolarization indices and decreased left ventricular function in CTRCD have not been elucidated. We closely assessed such relationships in patients with doxorubicin (DOX)-induced CTRCD.

METHODS

This retrospective, single-center, cohort study included 471 consecutive patients with malignant lymphoma who received chemotherapy including DOX. Of them, 17 patients with CTRCD and 68 patients without CTRCD who underwent 12‑lead electrocardiogram and an echocardiogram before and after chemotherapy were eventually analyzed. The fluctuations of the following electrocardiographic repolarization indices were evaluated in lead V5: QT, JT, T peak to T end interval (Tp-e), and activation recovery interval (ARI). These indices were corrected by heart rate with the Fridericia formula.

RESULTS

The median period from the end of chemotherapy to the diagnosis of the CTRCD group was 346 days (IQR 170-1283 days). After chemotherapy, the QT interval was significantly prolonged in both with and without CTRCD groups compared with that before chemotherapy (pre QTc vs. post QTc in CTRCD group, 386 ± 27 ms vs. 411 ± 37 ms, p = 0.03, pre QTc vs. post QTc in non-CTRCD group, 388 ± 24 ms vs. 395 ± 25 ms, p = 0.04, respectively). ARIc after chemotherapy was characteristically observed only in the CTRCD group (pre ARIc vs. post ARIc in CTRCD group, 258 ± 53 ms vs. 211 ± 28 ms, p = 0.03, pre ARIc vs. post ARIc in non-CTRCD group, 221 ± 19 ms vs. 225 ± 23 ms, NS, respectively) and had negative correlations with left ventricular ejection fraction (r = -0.56, p < 0.001). Using the receiver-operating characteristic curve, the relationship between ARIc and CTRCD morbidity was examined. The optimal cut-off point of ARIc prolongation between before and after chemotherapy was 18 ms (sensitivity 75 %, specificity 79 %, area under the curve 0.76).

CONCLUSIONS

ARIc prolongation may be useful in the early detection of developing late-onset chronic DOX-induced CTRCD and lead to early treatment for cardiac protection.

Early electrocardiographic indices for predicting chronic doxorubicin-induced cardiotoxicity

BACKGROUND

Dealing with chemotherapy-related cardiac dysfunction (CTRCD) remains a significant problem complicated by the difficulty in early detection of cardiotoxicity. Electrocardiogram (ECG) is expected to be the most realistic methodology due to lower cost-performance and non-invasiveness. We investigated the long-term visual fluctuations in the ECG waveforms in patients with chronic doxorubicin (DOX)-induced cardiotoxicity to identify ECG indices for the early detection of cardiotoxicity.

METHODS

We conducted a retrospective case series study by reviewing the medical records of 470 consecutive patients with malignant lymphoma who were treated with DOX at our institute between January 2010 and December 2017. Of them, 23 (4.9%) patients developed left ventricular dysfunction and were diagnosed with CTRCD using echocardiography. We assessed the ECG indices on 12-lead ECG recordings before and after treatment in 15 patients; eight patients were excluded due to conduction disturbances or atrial fibrillation.

RESULTS

CTRCD was detected at a median of 475 (interquartile range, IQR: 341-1333) days after initiating chemotherapy. The evaluation of ECG indices preceding CTRCD development was performed 93 (IQR: 52-232) days before the detection of CTRCD. In the stage of CTRCD, the most significant ECG change was T-wave flattening in leads V3-V6 (12 patients, 80%). Additionally, QTa prolongation was observed in leads I and aVL (n = 10, 66%), leads II, III, and aVF (n = 9, 60%), and leads V3-V6 (n = 10, 73%). These ECG changes were not observed before the treatment but were detected mildly in the pre-CTRCD stage, which subsequently worsened in the CTRCD stage.

CONCLUSIONS

This study indicated that T-wave changes and QTa prolongation may be useful as an early indicator before the onset of CTRCD in patients with DOX-induced cardiotoxicity.

The role of metabolic diseases in cardiotoxicity associated with cancer therapy: What we know, what we would know

Metabolic diseases, such as obesity and type 2 diabetes, are known risk factors for cardiovascular (CV) diseases. Thus, patients with those comorbidities could be at increased risk of experiencing cardiotoxicity related to treatment with Anthracyclines and the other new generation targeted anticancer drugs. However, investigations addressing the mechanisms underlying the development of CV complications and poor outcome in such cohort of patients are still few and controversial. Given the importance of a personalized approach against chemotherapy-induced cardiomyopathy, this review summarizes our current knowledge on the pathophysiology of chemotherapy-induced cardiomyopathy and its association with obesity and type 2 diabetes. Along with clinical evidences, future perspectives of preclinical research around this field and its role in addressing important open questions, including the development of more proactive strategies for prevention, and treatment of cardiotoxicity during and after chemotherapy in the presence of metabolic diseases, is also presented.

Prevalence of Major Cardiac Events of Anthracycline-Induced Cardiotoxicity in Southwestern Iran: Different Response Patterns to Cumulative Dose

Background:

Anthracyclines are widely used chemotherapeutic agents in several cancers. Since its use, survival improved significantly among cancer patients and has been reported to be up to 80%. However, anthracyclines possess several cardiac, renal and hematological toxicities which limit their use in practice. Cardiotoxicity is still the most important and dose-limiting side effect of anthracycline treatment. Here we aimed to investigate the frequency of anthracyclineinduced cardiomyopathy in pediatric malignancies in Khuzestan Province, Iran.

Methods:

A total of 112 patients were enrolled in the present study. Patients were allocated to the case or control group based on receiving anthracycline. Echocardiographic examinations were performed by a cardiologist. Electrocardiograms were also recorded.

Results:

We showed that cancer patients who underwent anthracycline treatment showed cardiomyopathy as defined by lower LVEF (Left Ventricular Ejection Fraction) among patients (p = 0.041). Abnormal LVEF was reported with a frequency of about 9.5% in patients (p = 0.026). However, LVFS (Left Ventricular Fraction Shortening), QRS voltage and QT interval did not differ significantly between treatment and control groups. Our data analysis revealed that this difference is mainly related to high cumulative dose since high cumulative dose of anthracycline (>300 mg/m2) leads to lower LVEF and LVFS and higher QRS voltage in comparison with lower cumulative dose (<300 mg/m2) and control group; but there was no significant difference between low dose and control group. Different age groups and type of malignancy including hematological and solid tumors did not show any significant differences for echocardiographic and electrocardiograms parameters.

Conclusion:

In our study, lower LVEF among patients who received anthracyclines were mainly related to a high cumulative dose of anthracyclines, which emphasizes the effect of cumulative dose for cardiotoxic effects. Larger studies are needed to investigate possible other risk factors for cardiotoxicity.

Remodeling of ventricular repolarization in experimental right ventricular hypertrophy

BACKGROUND

To understand electrophysiological mechanisms that underlie the progression of compensated right ventricular hypertrophy (RVH) to heart failure, the purpose of the study was to evaluate remodeling of ventricular repolarization in connection with hemodynamic abnormalities and vulnerability of the heart ventricles to arrhythmias in RVH rats with pulmonary arterial hypertension (PAH) and heart failure.

METHODS

PAH followed by heart failure was induced by monocrotaline in adult female Wistar rats. Unipolar epicardial electrograms and cardiac hemodynamic parameters were recorded in situ. Vulnerability to ventricular arrhythmias was measured as the threshold dose of aconitine required to produce sustained ventricular tachycardia. Histological examination of the heart ventricles was performed. Activation-recovery intervals (ARIs) and ARI dispersions were used as indices of durations and heterogeneity of repolarization respectively to assess ventricular repolarization.

RESULTS AND CONCLUSIONS

The development of compensated RVH was characterized by the dramatic prolongation of repolarization against the less expressed increase in repolarization heterogeneity, whereas the dramatic increase in repolarization heterogeneity against the less expressed but inhomogeneous prolongation of repolarization occurred in the progression of compensated RVH to heart failure. These changes increased vulnerability of the failing heart but not the compensated heart to aconitine-induced ventricular arrhythmias.

Right heart function deteriorates in breast cancer patients undergoing anthracycline-based chemotherapy

BACKGROUND

Cardiotoxicity from anthracycline-based chemotherapy is an important cause of early and late morbidity and mortality in breast cancer patients. Left ventricular (LV) function is assessed for patients receiving anthracycline-based chemotherapy to identify cardiotoxicity. However, animal studies suggest that right ventricular (RV) function may be a more sensitive measure to detect LV dysfunction. The purpose of this pilot study was to determine if breast cancer patients undergoing anthracycline-based chemotherapy experience RV dysfunction.

METHODS

Forty-nine breast cancer patients undergoing anthracycline-based chemotherapy at the Ottawa Hospital between November 2007 and March 2013 and who had 2 echocardiograms performed at least 3months apart were retrospectively identified. Right atrial area (RAA), right ventricular fractional area change (RV FAC) and RV longitudinal strain of the free wall (RV LSFW) were evaluated according to the American Society of Echocardiography guidelines.

RESULTS

The majority (48/49) of patients were females with an average age of 53.4 (95% CI: 50.1-56.7years). From baseline to follow-up study, average LV ejection fraction (LVEF) decreased from 62.22 (95% CI: 59.1-65.4) to 57.4% (95% CI: 54.0-60.9) (P=0.04). During the same time period, the mean RAA increased from 12.1cm(2) (95% CI: 11.1-13.0cm(2)) to 13.8cm(2) (95% CI: 12.7-14.9cm(2)) (P=0.02), mean RV FAC decreased (P=0.01) from 48.3% (95% CI: 44.8-51.74) to 42.1% (95% CI: 38.5-45.6%), and mean RV LSFW worsened from -16.2% (95% CI: -18.1 to -14.4%) to -13.81% (95% CI: -15.1 to -12.5%) (P=0.04).

CONCLUSION

This study demonstrates that breast cancer patients receiving anthracycline-based chemotherapy experience adverse effects on both right atrial size and RV function. Further studies are required to determine the impact of these adverse effects on right heart function and whether this represents an earlier marker of cardiotoxicity.

Epicardium Formation as a Sensor in Toxicology

Zebrafish (Danio rerio) are an excellent vertebrate model for studying heart development, regeneration and cardiotoxicity. Zebrafish embryos exposed during the temporal window of epicardium development to the aryl hydrocarbon receptor (AHR) agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exhibit severe heart malformations. TCDD exposure prevents both proepicardial organ (PE) and epicardium development. Exposure later in development, after the epicardium has formed, does not produce cardiac toxicity. It is not until the adult zebrafish heart is stimulated to regenerate does TCDD again cause detrimental effects. TCDD exposure prior to ventricular resection prevents cardiac regeneration. It is likely that TCDD-induced inhibition of epicardium development and cardiac regeneration occur via a common mechanism. Here, we describe experiments that focus on the epicardium as a target and sensor of zebrafish heart toxicity.