Effect of acute high-intensity interval exercise on a mouse model of doxorubicin-induced cardiotoxicity: a pilot study.

BACKGROUND: It is unknown whether high-intensity interval exercise (HIIE) may potentiate or attenuate the cardiotoxic effect of chemotherapy agents such as doxorubicin (DOX) when performed shortly after treatment. The study aimed to investigate the effect of acute HIIE on cardiac function and structure performed either 1, 2 or 3 days after DOX injection in an animal model. METHODS: Female C57bl/6 mice (n = 28), 70 days old, received a bolus 20 mg/kg intravenous tail vein DOX injection. Three exercise groups performed 1 HIIE session (16 sets of 1 min at 85-90% of peak running speed) at 1 (n = 7), 2 (n = 7), and 3 days (n = 8) following the DOX injection. A sedentary (SED) group of mice (n = 6) did not exercise. Animals underwent echocardiography under light anesthesia (isoflurane 0.5-1%) before and 7 days after the DOX injection. Animals were sacrificed on day 9 and hearts were collected for morphometric and histological analysis. RESULTS: Animals exercising on day 3 had the smallest pre-post reduction in left ventricular fractional shortening (LVFS) (MΔ= -1.7 ± 3.3; p = 0.406) and the SED group had the largest reduction (MΔ=-6.8 ± 7.5; p = 0.009). After reclassification of animals according to their exercise compliance (performing > 8/16 of high-intensity bouts), LVFS in compliant mice was unchanged over time (LVFS MΔ= -1.3 ± 5.6; p = 0.396) while non-compliant animals had a LVFS reduction similar to sedentary animals. There were no significant differences in myocardial histology between groups. CONCLUSIONS: In this pilot murine study, one single HIIE session did not exacerbate acute doxorubicin-induced cardiotoxicity. The timing of the HIIE session following DOX injection and the level of compliance to exercise could influence the negative impact of DOX on cardiac function.

Cardiac remodeling in amateur triathletes after 24 weeks of exercise training for a half-Ironman event: a brief report.

BACKGROUND: Triathletes' physiological adaptations to exercise training can have a different impact on cardiac remodeling based on the extreme exercise preparation. Moreover, cardiac remodeling might be different depending on whether triathletes have trained for many years or if they just decided to be more active. Nevertheless, data are limited in amateur endurance athletes and studies about them are key for their safety. Therefore, we investigated the effects of exercise training for a half-ironman on cardiac remodeling. METHODS: A total of 24 amateur athletes underwent a 24-week exercise program and were followed by three-dimensional echocardiography to assess its global impact on cardiac remodeling. Subanalyses were performed based on participants past-training experience (low versus high). RESULTS: We found significant group effects on the right and left ventricle, significant time effect on the right ventricle. No significant interaction effects were observed. We observed significant correlations between the right ventricle, clinical and performance characteristics where the peak power output explained 38% of the variance, while the body surface area, weight and power at the second ventilatory threshold explained 34%, 31% and 30%, respectively. CONCLUSIONS: Changes in cardiac remodeling in response to an exercise program for a half-ironman are not homogeneous across the ventricles and are influenced by participants' past-training experience. This study strengthens our knowledge of extreme exercise training for a half-ironman to further develop better training programs and medical follow-up in amateur triathletes.

Usefulness of low-dose dobutamine echocardiography to predict response and outcome in patients undergoing cardiac resynchronization therapy.

A substantial proportion of patients who meet the current guidelines for cardiac resynchronization therapy (CRT) fail to respond to this pacing modality. Although appropriate patient selection and left ventricular (LV) lead location have been ascribed as determinants of CRT response, the interaction among contractile reserve, dynamics of dyssynchrony, and lead location is not well understood. The present study prospectively evaluated the effect of contractile reserve and dobutamine-induced changes in LV synchrony, in relation to the LV lead location, as predictors of the response to CRT. In the present study, 31 patients were prospectively evaluated and underwent low-dose dobutamine echocardiography. The dobutamine-induced increase in ejection fraction (contractile reserve [CR]) was measured, and the most mechanically delayed segment was identified to classify patients into 2 groups. Group 1 had a CR of >20% and a LV lead position concordant with the mechanically delayed segment. Group 2 included the remaining patients (i.e., low CR, discordant LV lead position, or both). Patients in group 1 were significantly more likely to have an echocardiographic response at 6 months (80% of group 1 vs 29% of group 2, p = 0.018) and had an improved 2-year heart failure hospitalization-free survival rate (90% in group 1 vs 33% in group 2, p = 0.006). In conclusion, low-dose dobutamine echocardiography provides information that can help to predict responders to CRT. The response rates and heart failure hospitalization-free survival were improved in those patients with a CR >20% and an LV lead tip concordant with the most delayed mechanical segment.

Myocardial adaptation and efficiency in response to intensive physical training in elite speedskaters.

BACKGROUND: Physiological cardiac adaptations to exercise training resulting in the 'athlete's heart' are well known. Most of these studies, however, were included either those who exercise to exhaustion, non-elite athletes or those who participate primarily in sports requiring extensive weight training. Studies utilizing conventional and tissue Doppler echocardiographic studies in highly competitive elite athletes whose training includes both aerobic and weight training are limited. AIMS AND METHODS: 1) To identify baseline cardiovascular structural and physiologic adaptations present in elite athletes who participate in both endurance aerobic and weight training programs and to compare them to similarly aged sedentary controls. The population includes 24 speedskaters participating in the 2006 Olympic Games and 15 sedentary young subjects. 2) To evaluate possible structural and physiologic cardiac changes following short duration, vigorous exercise. We repeated the baseline echocardiographic protocol in the athletes following a 3000 m sprint conducted at race pace. RESULTS: Compared to non-athletes, the atrial and left ventricular (LV) volumes at rest were larger in elite athletes. There was enhanced LV diastolic function as manifested by higher early annular (septal and lateral) tissue Doppler velocities (E'): 12.7+/-2.3 vs 11.3+/-1.1 cm/s and 17.4+/-4.7 vs 14.4+/-1.2 cm/s, P=0.025 and 0.020 respectively. Evidence of right ventricular (RV) remodeling included larger basal RV dimensions (38+/-5 vs 32+/-4 mm, P=0.001), attenuated RV systolic function at rest (RV area change 35+/-13% in athletes vs 47+/-11% in controls, P=0.006) and lower RV systolic strain rate (SSR) 1.9+/-0.5 vs 2.9+/-1.1/s, P<0.001). However, there was better right ventricular (RV) diastolic function at rest, E': 13.5+/-3.6 vs 11.1+/-1.5 cm/s (P=0.016). Following exercise, the athletes exhibited augmentation of RV systolic function with increased RV fractional area change (increasing to 43+/-10%, P=0.007) and SSR (2.5+/-1.2/s post-exercise, P=0.038). CONCLUSION: Participation by world-class speedskaters in a vigorous training regimen results in cardiovascular anatomic and physiologic adaptations. These changes, including cardiac chamber dilatation, enhanced ventricular diastolic function and attenuated resting RV systolic function, are likely adaptive and allow for more efficient energy use at rest and a robust response to demands of exercise.

Integrating functional and anatomical information to facilitate cardiac resynchronization therapy.

Multiple imaging modalities are required in patients receiving cardiac resynchronization therapy. We have developed a strategy to integrate echocardiographic and angiographic information to facilitate left ventricle (LV) lead position. Full three-dimensional LV-volumes (3DLVV) and dyssynchrony maps were acquired before and after resynchronization. At the time of device implantation, 3D-rotational coronary venous angiography was performed. 3D-models of the veins were then integrated with the pre- and post-3DLVV. In the case displayed, prior to implantation, the lateral wall was delayed compared to the septum. The LV lead was positioned into the vein over the most delayed region, resulting in improved LV synchrony.

Echocardiographic measures of acute haemodynamic response after cardiac resynchronization therapy predict long-term clinical outcome.

AIMS: Although acute haemodynamic improvement in response to cardiac resynchronization therapy (CRT) is reflective of a favourable cardiac contractile response, there is limited information regarding not only its ability to predict long-term clinical outcome but also cardiac-substrate-specific differences in the prognostic value of this measure. METHODS AND RESULTS: Fifty-three heart failure patients (69 +/- 11 years) with low left ventricle ejection fraction (LVEF) (22 +/- 6%), wide QRS (169 +/- 31 ms), and indications for CRT were included. There were no significant differences in age, New York Heart Association (NYHA) class, medications, QRS width, or LVEF between ischaemic (n = 37) and non-ischaemic (n = 16) groups. Echocardiograms were performed within 24 h of implantation with device OFF and ON. Acute haemodynamic response was measured as LV dP/dt derived from the CW Doppler of mitral regurgitation. Percentage change in dP/dt was used to classify patients: high- (HR: DeltadP/dt > 25%) or poor-responders (PR: DeltadP/dt