Voluntary exercise does not affect stress-induced tachycardia, but improves resistance to cardiac arrhythmias in rats

1. It is currently unknown whether long-term voluntary exercise has enduring cardioprotective effects in animal models.

2. The present study was conducted in three groups of rats: (i) sedentary controls (n = 6); (ii) 24 h runners (n = 8; unlimited access to running wheels); and (iii) 2 h runners (n = 8; access to running wheels limited to 2 h daily). After termination of the 6 week exercise protocol, all rats were implanted with the telemetric electrocardiogram transmitters and were studied 1 week later.

3. Resting heart rate (HR) values in the control rats, 24 h runners and 2 h runners were 372 ± 7, 361 ± 9 and 298 ± 5 b.p.m., respectively (P < 0.05 for 2 h runners vs controls). The high-frequency spectral power in the control rats, 24 h runners and 2 h runners was 3.9 ± 0.2, 4.3 ± 0.3 and 5.3 ± 0.3 s2, respectively (P < 0.05 for 2 h runners vs controls), whereas intrinsic HR was 383 ± 3, 377 ± 2 and 346 ± 3 b.p.m., respectively (P < 0.001 for 2 h runners vs controls). Restraint stress provoked tachycardia of similar magnitude in all groups.

4. After completion of telemetric studies, haemodynamic indices and susceptibility to cardiac arrhythmias were assessed in anaesthetized animals, there were no major between-group differences in HR, arterial pressure, contractility indices or sensitivity to β-adrenoceptor stimulation (dobutamine) or blockade (atenolol). The effective refractory period in the control rats, 24 h runners and 2 h runners was 49 ± 2, 55 ± 2 and 60 ± 4 ms, respectively (P = 0.054 for 2 h runners vs controls). A significantly higher dose of aconitine was required to provoke ventricular arrhythmias in the 24 h and 2 h running groups compared with controls (489 ± 76, 505 ± 88 and 173 ± 33 μg, respectively; P < 0.05).

5. We conclude that, in rats, long-term voluntary exercise has enduring cardioprotective effects mediated at the level of both the central nervous system and the heart.

Clinical outcomes associated with screening and referral for depression in an acute cardiac ward

Aim.  The aim of this paper is to describe the implementation of a depression screening and referral tool in two cardiac wards of a major metropolitan public hospital. The tool consisted of two sections: (1) screening for depression risk (Cardiac Depression Scale-5) and (2) consequential referral actions.

Background.  Prior research has shown that depression in patients with heart disease is associated with significantly impaired quality of life, decreased medication adherence, increased morbidity and increased use of healthcare services.

Design.  A prospective in-patient study design.

Method.  A consecutive sample of 202 patients admitted to either the cardiac medical (n = 145) or surgical (n = 57) wards of a major Melbourne metropolitan hospital were recruited into the study over an 18-week period.

Results.  Just over half (54%) of the patients were identified as ‘at risk’ of depression. Of these, 19% were assessed as moderate risk and 35% high risk. Of those patients, 91% had the risk score documented in their medical history, 90% had engaged in discussions with clinicians regarding their risk score, 85% had their risk score communicated formally to the medical team and 25% were formally referred for appropriate follow-up – significantly more than prior to implementation of the screening and referral tool.

Conclusions.  By providing a formalised mechanism for detecting depression, documented screening and referral rates improved for those with comorbid depression and heart disease affording an opportunity for early intervention. These findings support a move towards integrated approaches to screening of depression to become standard practice in the acute cardiac setting.

Relevance to clinical practice.  Such mechanisms also have the potential to initiate the development of new models of care that acknowledge the complexity of comorbid depression and heart disease and provide pathways from speciality to primary care which integrate the physical and psychosocial domains inclusive of screening, referral, systematic monitoring and streamlined behavioural and physical care.

Impact of depression treatment on mental and physical health-related quality of life of cardiac patients : a meta-analysis

PURPOSE: To conduct a meta-analysis evaluating the effectiveness of depression treatment on mental and physical health-related quality of life (HRQOL) of cardiac patients.

METHODS: Studies were identified using medical, health, psychiatry, psychology, and social sciences databases. Inclusion criteria were (1) 1 or more control conditions, (2) random assignment to condition after admission for myocardial infarction (MI)/acute coronary syndrome, after recording positive results on a depression screener, (3) documentation of depression symptoms at baseline, (4) depression management as a component of the rehabilitation/intervention, (5) validated measure of HRQOL as an outcome, at minimum 6-month followup. For meta-analysis, mental and physical HRQOL were the end points studied, using standardized mean differences for continuous outcome measures, with 95% confidence intervals. Heterogeneity was explored by calculating I2 statistic.

RESULTS: Five randomized controlled trials included in the analysis represented 2105 participants (1058 intervention vs 1047 comparator). Compared with a comparator group at 6 months, a test for overall effect demonstrated statistically significant improvements in mental HRQOL in favor of the intervention (standardized mean differences = −0.29 [−0.38 to −0.20], [P < .00001]; I2 = 0%). Depression treatment had a modest yet significant impact on physical HRQOL (standardized mean differences = −0.14 [−0.24 to −0.04] [P = .009]; I2 = 15%).

CONCLUSION: While the impact of post-MI depression interventions on physical HRQOL is modest, treatment can improve mental HRQOL in a significant way. Future research is required to develop and evaluate a program that can achieve vital improvements in overall HRQOL, and potentially cardiovascular outcomes, of cardiac patients.

Metyrapone and fluoxetine suppress enduring behavioral but not cardiac effects of subchronic stress in rats

In humans, chronic stressors have long been recognized as potential causes for cardiac dysregulation. Despite this, the underlying mechanistic links responsible for this association are still poorly understood. The purpose of this study was to determine whether exposure to a paradigm of subchronic stress can provoke enduring changes on the heart rate of experimental rats and, if so, to reveal the autonomic and neural mechanisms that mediate these effects. The study was conducted on adult male Sprague-Dawley rats instrumented for telemetric recording of heart rate and locomotor activity. Animals were submitted to a subchronic stress protocol, consisting of a 1-h foot shock session on five consecutive days. Heart rate and locomotor activity were recorded continuously for 3 days before and for 6 days after the subchronic stress period. Subchronic foot shock produced significant and enduring reduction in heart rate both during the dark/active [Δ= −23 ± 3 beats per minute (bpm)] and light/inactive (Δ= −20 ± 3 bpm) phases of the circadian cycle, and a reduction in locomotor activity during the dark/active phase [Δ= −54 ± 6 counts per hour (cph)]. The bradycardic effect of subchronic stress was not related to a reduced locomotion. Selective sympathetic (atenolol) and vagal (methyl-scopolamine) blockades were performed to reveal which autonomic component was responsible for this effect. We found that the fall in heart rate persisted after subchronic stress in animals treated with atenolol (active phase Δ= −16 ± 3 bpm, inactive phase Δ= −19 ± 2 bpm), whereas vagal blockade with scopolamine transiently prevented this effect, suggesting that the bradycardia following subchronic stress was predominantly vagally mediated. Fluoxetine (selective serotonin reuptake inhibitor) and metyrapone (inhibitor of corticosterone synthesis) treatments did not affect heart rate changes but prevented the reduction in locomotion. We conclude that subchronic stress exposure in rats reduces heart rate via a rebound in vagal activation and that this effect is serotonin- and corticosterone-independent.

Attendance at cardiac rehabilitation is associated with lower all-cause mortality after 14 years of follow-up

Objective To investigate whether attendance at cardiac rehabilitation (CR) independently predicts all-cause mortality over 14 years and whether there is a dose–response relationship between the proportion of CR sessions attended and long-term mortality.

Design Retrospective cohort study.

Setting CR programmes in Victoria, Australia

Patients The sample comprised 544 men and women eligible for CR following myocardial infarction, coronary artery bypass surgery or percutaneous interventions. Participants were tracked 4 months after hospital discharge to ascertain CR attendance status.

Main outcome measures All-cause mortality at 14 years ascertained through linkage to the Australian National Death Index.

Results In total, 281 (52%) men and women attended at least one CR session. There were few significant differences between non-attenders and attenders. After adjustment for age, sex, diagnosis, employment, diabetes and family history, the mortality risk for non-attenders was 58% greater than for attenders (HR=1.58, 95% CI 1.16 to 2.15). Participants who attended <25% of sessions had a mortality risk more than twice that of participants attending ≥75% of sessions (OR=2.57, 95% CI 1.04 to 6.38). This association was attenuated after adjusting for current smoking (OR=2.06, 95% CI 0.80 to 5.29).

Conclusions This study provides further evidence for the long-term benefits of CR in a contemporary, heterogeneous population. While a dose–response relationship may exist between the number of sessions attended and long-term mortality, this relationship does not occur independently of smoking differences. CR practitioners should encourage smokers to attend CR and provide support for smoking cessation.