Editorial

Maximal exercise tolerance as a therapeutic end point in heart failure — Are we relying on the right measure?

Cardiac resynchronization therapy (CRT) devices not only deliver effective treatment but may also serve as valuable diagnostic tools in heart failure management. In the present study, the minutes of daily physical activity and heart rate variability, measured by sensors incorporated into such a device, reflected the effects of CRT and were related to New York Heart Association functional class.

The study was done to determine the prognostic importance of frequent ventricular ectopy in recovery after exercise among patients with systolic heart failure (HF).

Although ventricular ectopy during recovery after exercise predicts death in patients without HF, its prognostic importance in patients with significant ventricular dysfunction is unknown.

Systematic electrocardiographic data during rest, exercise, and recovery were gathered on 2,123 consecutive patients with left ventricular systolic ejection fraction ≤35% who were referred for symptom-limited metabolic treadmill exercise testing. Severe ventricular ectopy was defined as the presence of ventricular triplets, sustained or nonsustained ventricular tachycardia, ventricular flutter, polymorphic ventricular tachycardia, or ventricular fibrillation. The primary end point was all-cause mortality, with censoring for interval cardiac transplantation.

Of 2,123 patients, 140 (7%) had severe ventricular ectopy during recovery. There were 530 deaths (median follow-up among survivors 2.9 years). Severe ventricular ectopy during recovery was associated with an increased risk of death (three-year death rates 37% vs. 22%, hazard ratio [HR] 1.76; 95% confidence interval [CI] 1.32 to 2.34, p < 0.0001). After adjustment for ventricular ectopy at rest and during exercise, peak oxygen uptake, and other potential confounders, severe ventricular ectopy during recovery remained predictive of death (adjusted HR 1.48; 95% CI 1.10 to 1.97; p = 0.0089), whereas ventricular ectopy during exercise was not predictive of death in this cohort.

Severe ventricular ectopy during recovery after exercise is predictive of increased mortality in patients with severe HF and can be used as a prognostic indicator of adverse outcomes in HF cohorts.

Background: Target intensity-level of exercise training in patients with coronary artery disease is adjusted usually by a target heart rate (THR). This THR is aimed to be at or nearby the anaerobic threshold (AT) and is calculated commonly from parameters of regular exercise training, instead of an actual measurement of AT and its related heart rate. Therefore, this study evaluated whether a calculation is reliable. Methods: In 91 male patients (age 52±9 years) exercise capacity was measured after a recent (>4 weeks) coronary event. AT was compared with peak exercise capacity and heart rate at AT was compared with THR, using the Karvonen method. Results: Mean AT (18.2 ml/min/kg, range 9.2–32.2) and mean peak V_O2 (24.5, range 10.9–43.9) were slightly decreased (respectively 0.83 and 0.79 of predicted). When related to peak exercise capacity, AT showed a large inter-individual variation. For example, heart rate at AT ranged from 0.55 to 0.96 of peak heart rate. As a result heart rate at AT varied considerably with THR. The mean THR, although significantly higher, correlated well with mean heart rate at AT (respectively, 109 and 105/min, P<0.01; r=0.86, P<0.001). However, in an important number of patients heart rate at AT was more than 10% below or above THR (respectively, 30 and 7%). Conclusion: In individual exercise prescription for cardiac rehabilitation the training level should be determined directly, and not indirectly by calculation from heart rate parameters of exercise testing.

Internal atrial defibrillation (IAD) is able to restore sinus rhythm in patients with chronic atrial fibrillation (AF) and failed external electrical and/or pharmacologic cardioversion. To assess whether cardiorespiratory and hemodynamic function improve after IAD, 35 patients were prospectively investigated during constant workload exercise by spiroergometry and Doppler echocardiography before IAD, and 1 day and 1 month after IAD. Oxygen uptake kinetics, ventilation, left atrial mechanical function, and pulmonary artery pressure were determined simultaneously at rest and during steady state. During the serial follow-up, 20 patients maintained sinus rhythm. The time interval for achieving the steady state (146 ± 53 vs 132 ± 42 seconds; p = 0.5) and the oxygen deficit (645 ± 190 vs 670 ± 174 ml; p = 0.7) were not different before and 1 day after IAD, but decreased significantly after 1 month (98 ± 16 seconds, p = 0.01 and 487 ± 72 ml, p = 0.02). Exercise pulmonary artery systolic pressures were 38 ± 13 mm Hg before IAD, increased significantly to 46 ± 11 mm Hg on day 1 (p = 0.03), and decreased below baseline values at 1 month to 31 ± 12 mm Hg (p = 0.07). Peak A-wave velocities increased from 0.51 ± 0.1 m/s after 1 day to 0.67 ± 0.2 m/s after 1 month (p = 0.03). Restoration of sinus rhythm in patients with AF resistant to external electrical and/or pharmacologic cardioversion improves hemodynamic and cardiorespiratory function at daily activity exercise levels.