Myocardial energetics in dilated cardiomyopathy

Prognostic value of cardiac cycle efficiency in children undergoing cardiac surgery: a prospective observational study

BACKGROUND

Cardiac cycle efficiency (CCE) derived from a pressure-recording analytical method is a unique parameter to assess haemodynamic performance from an energetic view. This study investigated changes of CCE according to an anatomical diagnosis group, and its association with early postoperative outcomes in children undergoing cardiac surgery.

METHODS

Ninety children were included with a ventricular septal defect (VSD; n=30), tetralogy of Fallot (TOF; n=40), or total anomalous pulmonary venous connection (TAPVC; n=20). CCE along with other haemodynamic parameters, was recorded from anaesthesia induction until 48 h post-surgery. Predictive CCE (CCE_p) was defined as the average of CCE at post-modified ultrafiltration and CCE at the end of surgery. The relationship between CCE and early outcomes was assessed by the comparison between the high-CCE_p group (CCE_p ≥75th centile) and the low-CCE_p group (CCE_p ≤25th centile).

RESULTS

There was a significant time × diagnostic group interaction effect in the trend of CCE. Compared with the high-CCE_p group (n=23), the low-CCE_p group (n=22) required more inotropics post-surgery, had higher lactate concentrations at 8 and 24 h post-surgery, a longer intubation time and longer ICU stay, and higher frequency of peritoneal fluid.

CONCLUSIONS

Perioperative changes of CCE vary according to anatomical diagnosis in children undergoing cardiac surgery. Children with TOF have an unfavourable trend of CCE compared with children with VSD or TAPVC. A decline in CCE is associated with adverse early postoperative outcomes.

CLINICAL TRIAL REGISTRATION

ChiCTR1800014996.

Catecholamines restore myocardial contractility in dilated cardiomyopathy at the expense of increased coronary blood flow and myocardial oxygen consumption (MvO2cost of catecholamines in heart failure)

To investigate the metabolic cost of catecholamine use in heart failure, we administered intravenous dobutamine or norepinephrine to dogs with moderate and severe LV dysfunction until LV contractile function was restored to normal levels. Both drugs were associated with significant increases in myocardial O(2) consumption, increased coronary blood flow requirements and decreased myocardial mechanical efficiency. These mechanisms may contribute to the deleterious effects of catecholamines in heart failure.

Acute effects of a single low oral dose of pimobendan on left ventricular systolic and diastolic function in patients with congestive heart failure

A recent long-term multicenter trial has shown that pimobendan is more effective when administered in low doses. However, no data are available concerning the effect of a low dose of pimobendan on the systolic and diastolic pressure-volume relations in patients with heart failure. Therefore we examined the effects of a single low dose of oral pimobendan, a calcium sensitizer, on systolic and diastolic hemodynamics in patients with cardiomyopathy and congestive heart failure. We measured the left ventricular (LV) pressure-volume relations using a conductance catheter with a micromanometer tip in 10 patients with chronic congestive heart failure resulting from idiopathic cardiomyopathy before and 45 and 90 min after administration of a single oral dose of 2.5 mg of pimobendan. End-systolic elastance was used as an index of LV contractility and was measured during transient occlusion of the inferior vena cava. End-systolic elastance increased significantly by 25% at 45 min (p < 0.05) and by 55% at 90 min (p < 0.01) without an increase in myocardial oxygen consumption. The inotropic effect was accompanied by improved ventriculoarterial coupling. This effect was attenuated in patients with severely impaired myocardial contractility. LV relaxation, assessed by the time constant of isovolumic pressure decay (T(1/2)), was significantly shortened at 90 min (from 47.7 +/- 1.9 to 41.2 +/- 1.7 ms; p < 0.01), although it remained unchanged at 45 min. The diastolic pressure-volume relation showed a leftward and downward shift in all patients. These results indicate that low-dose oral pimobendan had favorable short-term inotropic and lusitropic effects in patients with congestive heart failure caused by idiopathic dilated cardiomyopathy, and may thus be a useful alternative to traditional agents. Further study in a large-scale trial is merited.

Effects of pimobendan, its active metabolite UD-CG 212, and milrinone on isolated blood vessels

The effects of pimobendan, 2-(4-hydroxy-phenyl)-5-(5-methyl-3-oxo-4,5-dihydo-2H-6-pyridazinyl ) benzimidazole (UD-CG 212), and milrinone were investigated on isometric contraction of vascular preparations in rats and guinea-pigs. The drugs dose dependently relaxed aortic, carotid and femoral arterial and mesenteric venous preparations precontracted with KCl or norepinephrine. The rank order of potency (negative log EC50 value) for these drugs was dependent upon the sources of the preparations and stimulants used. The relaxation response to milrinone was reversible, that to UD-CG 212 was poorly reversible, and that to pimobendan was intermediate. Relaxation responses to cromakalim were inhibited by 0.1 microM glibenclamide, whereas those to pimobendan, UD-CG 212 and milrinone were inhibited by glibenclamide only at doses as high as 10-30 microM. The drugs potentiated the relaxation response to isoproterenol but not glyceryl trinitrate, and noncompetitively inhibited arterial contractions accompanied by voltage-dependent Ca2+ influxes. It is suggested that the drugs are potent vasorelaxants, acting directly on vascular smooth muscle and that the vasorelaxant effects are mediated through cyclic AMP-dependent mechanisms.

Effect of enoximone alone and in combination with metoprolol on myocardial function and energetics in severe congestive heart failure: improvement in hemodynamic and metabolic profile

The hemodynamic and myocardial metabolic effects of enoximone (phosphodiesterase III inhibitor), alone or in combination with metoprolol (beta-adrenergic blocker), were studied in patients with congestive heart failure. Ten patients (New York Heart Association Class III-IV) underwent right heart and coronary sinus catheterization, and parameters were assessed at basal condition, at peak enoximone response (mean intravenous loading dose = 2.2 mg/kg), and after the combination with metoprolol (mean intravenous dose = 8.5 mg). Heart rate tended to increase during enoximone administration (from 102 +/- 16 to 107 +/- 16 min-1, ns) and was reduced during enoximone plus metoprolol (to 88 +/- 15 min-1, p < 0.05 vs. basal). Cardiac index was increased during enoximone (from 2.2 +/- 0.2 to 3.8 +/- 0.5 1/min/m2, p < 0.05) and decreased during enoximone plus metoprolol (to 2.8 +/- 0.5 1/min/m2, p < 0.05 vs. enoximone). Mean pulmonary wedge pressure fell during enoximone and remained reduced during enoximone plus metoprolol (from 27 +/- 9 to 9 +/- 3 and to 13 +/- 4 mmHg, respectively, both p < 0.05). Myocardial oxygen consumption did not change during enoximone (from 27 +/- 8 to 25 +/- 13 ml/min, ns) and was reduced during enoximone plus metoprolol (to 19 +/- 8 ml/min, p < 0.05 vs. basal). Myocardial lactate extraction tended to be lower during enoximone and during enoximone plus metoprolol conditions (from 38 +/- 17% to 26 +/- 20% and to 29 +/- 24%, respectively), but no statistical significance was found. Myocardial efficiency was increased during enoximone and during enoximone plus metoprolol (from 9 +/- 3% to 15 +/- 6% and to 14 +/- 6%, respectively, both p < 0.05). Thus in patients with congestive heart failure enoximone improves hemodynamics and, in most cases, it does not influence energetics. The addition of metoprolol to enoximone reduces heart rate, cardiac index, and myocardial oxygen consumption without any other major changes, producing a more physiologic hemodynamic and metabolic profile.