Impairment of left ventricular function during maximal isometric dead lifting

Atrial fibrillation is associated with decreased cardiac sympathetic response to isometric exercise in CHF in comparison to sinus rhythm

BACKGROUND

The presence of atrial fibrillation (AF) in congestive heart failure (CHF) is accompanied by increased mortality, although the exact mechanism is unclear. In previous studies, we have demonstrated cardiac baroreceptor abnormalities in association with AF and CHF. In this study, we sought to examine the effect of cardiac rhythm on the cardiac sympathetic response to exercise in CHF.

METHODS

In 13 CHF patients (six AF, seven SR, left ventricular ejection fraction 31 +/- 2%, age 61 +/- 1 years), we measured the hemodynamic and cardiac sympathetic response isometric handgrip (IHG) exercise.

RESULTS

At baseline the groups were well matched. Baseline hemodynamics and cardiac sympathetic activity did not significantly differ between the cohorts. In response to IHG exercise, both groups demonstrated significant hemodynamic responses. In conjunction, the sinus rhythm (SR) group demonstrated a significant increase in cardiac sympathetic response to exercise (P = 0.04) while in contrast the AF group did not (P = 0.6).

CONCLUSION

In this study, we demonstrate for the first time that the combination of AF and CHF is accompanied by a marked attenuation of the cardiac sympathetic response to acute hemodynamic stress. This implies AF is associated with a further impairment of baroreceptor response in CHF compared to SR. These findings present possible insights to the associated increased mortality and pathogenesis of AF with CHF.

The athlete's heart. A meta-analysis of cardiac structure and function

BACKGROUND

It has been postulated that depending on the type of exercise performed, 2 different morphological forms of athlete's heart may be distinguished: a strength-trained heart and an endurance-trained heart. Individual studies have not tested this hypothesis satisfactorily.

METHODS AND RESULTS

The hypothesis of divergent cardiac adaptations in endurance-trained and strength-trained athletes was tested by applying meta-analytical techniques with the assumption of a random study effects model incorporating all published echocardiographic data on structure and function of male athletes engaged in purely dynamic (running) or static (weight lifting, power lifting, bodybuilding, throwing, wrestling) sports and combined dynamic and static sports (cycling and rowing). The analysis encompassed 59 studies and 1451 athletes. The overall mean relative left ventricular wall thickness of control subjects (0.36 mm) was significantly smaller than that of endurance-trained athletes (0.39 mm, P=0.001), combined endurance- and strength-trained athletes (0.40 mm, P=0.001), or strength-trained athletes (0.44 mm, P<0.001). There was a significant difference between the 3 groups of athletes and control subjects with respect to left ventricular internal diameter (P<0. 001), posterior wall thickness (P<0.001), and interventricular septum thickness (P<0.001). In addition, endurance-trained athletes and strength-trained athletes differed significantly with respect to mean relative wall thickness (0.39 versus 0.44, P=0.006) and interventricular septum thickness (10.5 versus 11.8 mm, P=0.005) and showed a trend toward a difference with respect to posterior wall thickness (10.3 versus 11.0 mm, P=0.078) and left ventricular internal diameter (53.7 versus 52.1 mm, P=0.055). With respect to cardiac function, there were no significant differences between athletes and control subjects in left ventricular ejection fraction, fractional shortening, and E/A ratio.

CONCLUSIONS

Results of this meta-analysis regarding athlete's heart confirm the hypothesis of divergent cardiac adaptations in dynamic and static sports. Overall, athlete's heart demonstrated normal systolic and diastolic cardiac functions.

Acute responses to resistance training and safety

Resistance training is widely used in fitness programs for healthy individuals of all ages and has become accepted as part of the exercise rehabilitation process for patients with coronary artery disease. It is only during the past decade that the acute circulatory responses to resistance exercise have been investigated directly, using intra-arterial measurement techniques and two-dimensional echocardiography. This review examines the factors that influence the acute circulatory responses to resistance training. These include the number of repetitions, the absolute and relative load, the muscle mass engaged in the lifting, the joint angle, and the Valsalva maneuver. There is discussion of the responses in patients with coronary artery disease and the effects of resistance training on the acute responses. The review ends with a discussion of the safety of this form of exercise and concludes that it is safe and appropriate for most healthy individuals and many of those with different diseases.

Angiotensin-converting enzyme inhibition, autonomic activity, and hemodynamics in patients with heart failure who perform isometric exercise

Effects of angiotensin-converting enzyme inhibition (ACEI) on autonomic responses and hemodynamics in patients with congestive heart failure (CHF) subjected to isometric exercise have not been studied. We tested whether acute ACEI might influence the effects of isometric exercise in patients with CHF. In the first part of the study we showed that isometric exercise increased blood pressure in the control group and in the CHF group, whereas cardiac output increased only in the control group. Stroke volume remained unchanged in the control group, whereas it decreased significantly in CHF group. We next analyzed the effect of acute ACEI (5 mg ramipril) on the decrease in cardiac output during isometric stress in patients with CHF. During isometric exercise mean blood pressure and heart rate increased similarly in both groups. However, cardiac output decreased during placebo by -0.48 +/- 0.12 L/min (p < 0.01) but not during ACEI. Spectral analysis of blood pressure showed an increase (p < 0.01) in the high-frequency parasympathetic component from 7.3% +/- 3.6% to 18.1% +/- 9.5% after ACEI. norepinephrine plasma levels increased after isometric stress in the placebo group, whereas other hormones did not change. ACEI prevented the norepinephrine increase after isometric stress. Thus the decrease in cardiac output during isometric exercise in patients with CHF was prevented by acute ACEI. The effect of ACE inhibition may be related to reduced sympathetic activity.

Continuous measurement of blood pressure, heart rate and left ventricular performance during and after isometric exercise in head-out water immersion

Experiments were performed to determine the changes in blood pressure (BP), heart rate (HR) and left ventricular function during and after isometric knee extension during thermoneutral (35 degrees C) head-out water immersion (HWI) or in air. Seven healthy male subjects mean age 24 (SD 3) years kept their knees extended (60% maximal voluntary extension) until they reached exhaustion. The mean BP at rest was 80 (SD 10) and 78 (SD 8) mmHg [10.7 (SD 1.33) and 10.4 (SD 1.07)kPa] in air and during HWI, respectively, (NS). They increased progressively (P < 0.01) during contraction and reached maximal values of 148 (SD 22) and 143 (SD 26) mmHg [19.7 (SD 2.93) and 19.1 (SD 3.47)kPa] in air and in HWI, respectively, (NS). The mean HR at rest was 74 (SD 8) and 70 (SD 11) beats.min-1 in air and in HWI, respectively, (NS). They also increased progressively, (P < 0.01) and reached 126 (SD 14) and 118 (SD 17) beats.min-1 in air and in HWI, respectively, (NS). The changes in BP and HR during contraction in HWI tended to be smaller than those in air (NS). Left ventricular end diastolic diameters (dd) at rest in HWI were greater than those in air and were maintained at higher values during and after isometric contraction. In contrast, dd decreased during isometric contraction in air (P < 0.01). The change of left ventricular systolic diameters (ds) in HWI was no different to those in air. From these findings, isometric exercise in thermoneutral HWI would seem to be characterized by a greater dd than in air and this could be useful for patients with deconditioning effects such as orthostatic hypotension.

Continuous measurement of left ventricular performance during and after maximal isometric deadlift exercise

BACKGROUND

Isometric exercise produces a reflex increase in arterial blood pressure that is proportional to the intensity and mass of muscle used during contraction. Little is known about the transient effects of heavy weight lifting on left ventricular performance. In this study, we measured continuous changes in left ventricular performance during maximal large-muscle isometric exercise using the standing deadlift position.

METHODS AND RESULTS

Ten healthy young men performed serial deadlifts at 50% of maximal voluntary effort for 90 seconds and 100% of maximal effort for 30 seconds. Echocardiographic imaging (apical four-chamber view), arterial blood pressure (brachial artery catheter), and electrocardiographic monitoring were recorded throughout the deadlift and for 30 seconds of recovery. Aortic flow velocity was also monitored during a separate series of deadlifts. During 100% maximal deadlift, mean arterial pressure increased from 108 +/- 4 to 164 +/- 6 mm Hg. Left ventricular ejection fraction declined initially (from 57 +/- 2% to 49 +/- 3%) at 15 seconds into the lift and recovered (56 +/- 1%) due to significant increases in end-diastolic volume (104 +/- 11 ml to 132 +/- 16 ml) by the end of the lift. The peak systolic pressure/end-systolic volume ratio did not change during the deadlift. After cessation of the deadlift, mean arterial pressure declined precipitously (to 88 +/- 4 mm Hg) within 5 seconds and gradually returned to baseline after 30 seconds. Left ventricular performance indexes all increased significantly during the recovery phase (ejection fraction to 68 +/- 3%, peak systolic pressure/end-systolic volume ratio to 5.9 +/- 0.9). Findings were qualitatively similar for the 50% deadlift.

CONCLUSIONS

During an intense isometric deadlift, left ventricular performance declines initially but is restored by the Frank-Starling mechanism. Upon release of the deadlift, increased left ventricular performance develops in conjunction with a rapid decrease in arterial pressure. The combined effects of increased wall stress during the lift phase and enhanced contractility during the release phase probably contribute to left ventricular hypertrophy associated with repetitive weight training.