Sympathetic activity in children undergoing balloon valvuloplasty of pulmonary stenosis

Alpha blocker and angiotensin-converting enzyme inhibitor in the management of severe pulmonary valve stenosis: from bench to bedside

INTRODUCTION

Neonates with severe pulmonary valve stenosis tend to remain oxygen dependent, despite resolution of the transpulmonary gradient. Alpha 2 blockers – phentolamine – and angiotensin-converting enzyme inhibitors – captopril – were reported to improve oxygen saturation.

OBJECTIVE

To describe the role of phentolamine and captopril in the treatment of these patients.

METHODS

In a retrospective cohort study, 28 neonates with severe pulmonary valve stenosis underwent balloon valvuloplasty. Among them, 20 remained oxygen or prostaglandin dependent after intervention, and were treated with phentolamine or captopril. Oxygen saturation was monitored before and after intervention and following treatment with these medications. Mean duration of hospitalisation was recorded.

RESULTS

Mean age and weight were 25.2 days and 3.1 kg, respectively. Before balloon dilation, 18/20 (90%) neonates were on prostaglandin, whereas after the procedure only 6/18 patients required it. All 20 patients required oxygen after the procedure, and nine patients (45%) were started on phentolamine. Among them, one patient with severe infundibular stenosis did not respond favourably, and 11 patients (55%) were started on captopril. After starting phentolamine or captopril treatment, prostaglandin could be discontinued after a mean time of 15.86 hours. Within <2 days, there was an increase in mean oxygen saturation from 76.6 to 93.0%.

CONCLUSION

Phentolamine and captopril seem to have therapeutic roles in neonates with severe pulmonary valve stenosis who remain oxygen dependent after balloon dilation. Both drugs led to vasodilation of the pulmonary and systemic vascularisation and facilitated inflow to the right ventricle. Right-to-left shunt across a patent foramen ovale or atrial septal defect decreased and saturation improved, leading to a significant reduction in the length of hospitalisation.

Angiotensin converting enzyme inhibitor as an additive treatment after successful balloon dilation of a critical pulmonary valve stenosis

A 2 days old, 2.7 kg heavy baby boy with critical pulmonary stenosis, underwent successful balloon dilation. After the uneventful procedure, he remained oxygen dependent. The baby was given oral angiotensin converting enzyme inhibitor (ACE inhibitor), instead of an infusion of alpha blocker. Within few hours, in the afternoon of the same day after administration of ACE Inhibitor, the baby could be weaned off oxygen, maintaining on room air, oxygen saturation between 87% and 92%. At follow-up, two months later, his saturation was 99% on room air. We believe that some neonates with critical pulmonary valve stenosis who remain oxygen dependent despite successful balloon dilation, could benefit from such management.

Sympathetic overactivity in patients with pulmonary stenosis and improvement after percutaneous balloon valvuloplasty

OBJECTIVE

Percutaneous balloon valvulotomy (PBV) is the procedure of choice for the treatment of valvular pulmonary stenosis (PS) with similar results comparable to surgical valvotomy but less invasive.

METHODS AND RESULTS

Twenty-seven consecutive patients with PS being evaluated for PBV were enrolled in the study. Peak instantaneous transvalvular gradient, right ventricle (RV) diameter, mean atrial pressures, RV systolic pressure (RVSP), pro-brain natriuretic peptide (proBNP) levels significantly decreased immediately after PBV. Regarding heart rate variability (HRV) parameters, mean HR (heart rate), LF (low frequency) day and night, LF/HF day and night significantly decreased and standard deviation of all NN intervals (SDNN), root mean square of successive differences (RMSSD), P number of NN intervals that differed by more than 50 ms from adjacent interval divided by the total number of all NN intervals (PNN50), HF (High frequency) day and night significantly increased 1 day after PBV and these changes were shown to be preserved at the first month. The increase in SDNN was correlated with the decrease in right atrial pressure (RAP) (r =-0.5, P = 0.04); the increase in standard deviation of the 5-minute mean RR intervals (SDANN) was correlated with the decrease in proBNP (r =-0.4, P = 0.03).

CONCLUSIONS

Sympathetic overactivity and increased proBNP levels were associated with the symptomatic status of patients with PS. Associated with a decrease in atrial pressures and proBNP levels, PBV yielded a decrease in adrenergic overactivity in the patients with PS.

Phentolamine as a treatment for poor mixing in transposition of the great arteries with adequate intraatrial communication

Patients with transposition of the great arteries often show poor mixing for different reasons, even after adequate balloon atrial septostomy. We present a patient with such a lesion whose clinical status improved dramatically after phentolamine was applied. We believe this improvement is due to reduction in afterload caused by the alpha(2) blocker and also possibly as a response to a presumptive effect of the drug on the diastolic function of the right ventricle, allowing more left-to-right shunt across the atrial septal defect. Both phenomena can improve cardiac output in such a situation.

Receptor crosstalk. Implications for cardiovascular function, disease and therapy

There are at least three well-defined signalling cascades engaged directly in the physiological regulation of cardiac circulatory function: the beta1-adrenoceptors that control the cardiac contractile apparatus, the renin-angiotensin-aldosterone system involved in regulating blood pressure and the natriuretic peptides contributing at least to the factors determining circulating volume. Apart from these pathways, other cardiac receptor systems, particularly the alpha1-adrenoceptors, adenosine, endothelin and opioid receptors, whose physiological role may not be immediately evident, are also important with respect to regulating cardiovascular function especially in disease. These and the majority of other cardiovascular receptors identified to date belong to the guanine nucleotide binding (G) protein-coupled receptor families that mediate signalling by coupling primarily to three G proteins, the stimulatory (Gs), inhibitory (Gi) and Gq/11 proteins to stimulate the adenylate cyclases and phospholipases, activating a small but diverse subset of effectors and ion channels. These receptor pathways are engaged in crosstalk utilizing second messengers and protein kinases as checkpoints and hubs for diverting, converging, sieving and directing the G protein-mediated messages resulting in different signalling products. Besides, the heart itself is endowed with the means to harmonize these signalling mechanisms and to fend off potentially fatal consequences of functional loss of the essential signalling pathways via compensatory reserve pathways, or by inducing some adaptive mechanisms to be turned on, if and when required. This receptor crosstalk constitutes the underlying basis for sustaining a coherently functional circulatory entity comprising mechanisms controlling the contractile apparatus, blood pressure and circulating volume, both in normal physiology and in disease.

Phentolamine improves clinical outcome after balloon valvoplasty in neonates with severe pulmonary stenosis

Two neonates with severe pulmonary stenosis deteriorated immediately after successful balloon valvoplasty as a result of increased infundibular obstruction. They were treated with beta-adrenoceptor blockers and intravascular expansion with limited success. Phentolamine was then given, resulting in dramatic improvement. The children could be weaned from the ventilator within hours of starting this new therapeutic modality.