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As new treatment strategies are developed which outperform previous approaches in terms of safety, efficacy and long-term results, a reappraisal of old therapeutic dogmas is warranted, including lowering the threshold for intervention. Pulmonary valvuloplasty was introduced in 1982 to treat children and adults with significant isolated pulmonary valve stenosis (PS) and provided a very reliable tool to treat the problem avoiding cardiac surgery, with very good long-term results in terms of reinterventions as well as functional outcomes.1 ,2
Besides the neonate with critical PS, the same technique has been used to treat older children and adults with isolated PS. In these latter patient groups, the physiopathological mainstay behind the recommendation for treatment is that significant PS (defined as a Doppler velocity >4.0 m/s) creates such a significant afterload resistance and right ventricular (RV) hypertension that the RV is not able to increase stroke volume during exercise as it should. Additionally, RV hypertrophy and stiffness related to structural alterations, small infarcts and fibrosis limits ventricular preload, causing a significant drop in RV end diastolic volume during exercise and a blunted RV stroke volume response. Ultimately, these changes limit exercise capacity and cause symptoms.3 ,4 As such, severe PS is not associated with a good prognosis if left untreated.
Conversely, the available evidence suggests that the natural history of mild and moderate isolated PS beyond infancy is good even in the absence of treatment when patients are asymptomatic. Current guidelines support a watchful approach in asymptomatic adults with maximal Doppler echo velocities <4.0 m/s, in the absence of other consequences like arrhythmias.5 However, if a reasonable case was made that even non-significant PS could be associated with a substantial handicap in the cardiovascular adaptation to exercise, treatment in some cases might then be supported by such deviations from normal cardiovascular physiology. However, investigations into cardiovascular exercise adaptation in people with native isolated PS is limited by small numbers, and the inclusion on patients with moderate6 or severe degrees of PS.3 ,4 In their study, Krabill and colleagues included 24 adults with isolated native PS, nine of whom had moderate PS (baseline right ventricular systolic pressure of 37±8 mm Hg). In those patients, by means of exercise invasive monitoring, they noted a slight increase in RV end diastolic pressure during exercise (suggestive of restrictive RV physiology), with flat stroke volume response. Cardiac output nearly doubled and this was achieved by increasing heart rate. In a recent publication, Romeih studied 11 adults with native isolated PS of mild to moderate degree (maximal pulmonary valve Doppler gradient 38±4 mm Hg) by means of cardiopulmonary exercise test and dobutamine stress MRI.6 In this patient group, the authors noted a clinically significant increase of stroke volume and cardiac output with dobutamine infusion. Importantly, exercise peak workload and peak oxygen uptake were entirely normal.6 Reassuringly, none of their patients showed evidence of myocardial scarring.
Meester and colleagues7 provide some more insight into exercise adaptation of adults with native mild and moderate PS. Meester and colleagues studied 19 adults, with 15 patients out of 19 (79%) having mild, and 4 having moderate PS. As expected, Doppler gradient doubled during exercise. The authors found that peak workload and peak oxygen uptake were reduced when compared with normal matched subjects. This finding would be sufficient to cause excitement in many interventional cardiologists but not in the authors of the study, and rightly so. After careful analysis and dissection of the data, the authors correctly conclude that the different exercise capacity was largely not due to a difference in cardiac adaptation to exercise. Indeed, indexes of cardiac adaptation to exercise, like the relationship between oxygen uptake and oxygen pulse and workload, as well as the kinetic of oxygen pulse during exercise (a non-invasive correlate of stroke volume) were indiscernible from normal. The authors also demonstrated that baseline heart rate, as well as heart rate reserve, were lower in patients than in healthy controls. The latter findings, and the ratio between workload reached at the anaerobic threshold, and the one reached at peak exercise (42% in patients vs 56% in healthy matches) showing early anaerobic threshold, further suggest that reduced fitness level seems to be the main cause of reduced exercise capacity in this cohort. Unfortunately, objective information on the fitness level of the study subjects was not available in this study. This clearly represents an area for further research. Despite this limitation, the findings of the study seem to support the recommendation for no valve intervention in this group. This watchful approach seems to be also warranted when considering that pregnancy seems to be safe and well tolerated, from a cardiac point of view, in women with mild and moderate isolated pulmonary stenosis, as noted by Drenthen et al.8 This is particularly relevant as the haemodynamic burden of pregnancy (increase in circulating volume and cardiac output, increase in heart rate and decrease in vascular resistance) mimics most of the changes observed during exertion, and deterioration in previously stable women was observed only in symptomatic severe pulmonary stenosis. Despite the good course into the 4th decade of life, longer-term studies focusing on RV haemodynamics and function are required in order to confirm that mild/moderate PS remains indeed a benign lesion over the course of the entire life.
The study by Meester is important also because it reminds us how important regular physical activity is, particularly in individuals with congenital heart disease, where several factors, including parental protection and physicians uncomfortable with providing formal exercise recommendations can lead to adults who do not engage in regular and appropriate physical activity. Indeed, the work by Meester stresses how important it is to consider fitness levels when making assumptions about the potential causes of exercise limitation in patients with congenital heart disease. Furthermore, the lack of regular physical activity has far larger health consequences, which have been thoroughly explained elsewhere.9 As the measurement of fitness level is not simple in clinical practice, one pragmatic and positive solution would be to ensure that our patients comply with the intensity, frequency and duration of physical activity that is recommended depending on their heart defect,9 as this is not only associated with higher exercise capacity but also with significant general health benefits.
Asymptomatic adults with mild/moderate PS might need a balloon after all, but rolling on the ground with them chasing after it and not one floating in their heart.
Footnotes
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Contributors Both authors have read the submitted manuscript and have no Competing interests to disclose.
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Competing interests None.
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Provenance and peer review Commissioned; internally peer reviewed.