Mechanisms of exercise-induced pulmonary hypertension in patients with cardiac septal defects

Pulmonary Function in Older Patients With Ventricular Septal Defect

To better understand the evolvement of the pulmonary dysfunction in the aging ventricular septal defect (VSD) patient, we invited adult patients with a congenital VSD and healthy age- and gender-matched controls for static and dynamic spirometry, impulse oscillometry, multiple breath washout, and diffusion capacity for carbon monoxide testing. Primary outcome was forced expiratory volume in 1 second. In total, 30 patients with a surgically corrected VSD (mean age 51 ± 8 years), 30 patients with a small, unrepaired VSD (mean age 55 ± 1 years), and 2 groups of 30 age- and gender-matched, healthy controls (mean age 52 ± 9 years and 55 ± 10 years, respectively) were included. Median age of radical surgery was 6.3 (total range: 1.4 to 54) years and median follow-up after surgery was 40 years (total range: 3.4 to 54). Compared with healthy matched controls, surgically corrected VSD patients had lower forced expiratory volume in 1 second, 87 ± 19% versus 105 ± 14% of predicted, p <0.01, lower forced vital capacity, 92 ± 16% versus 107 ± 13% of predicted, p <0.01, and lower peak expiratory flow, 100 ± 21% versus 122 ± 16% of predicted, p <0.01. Furthermore, corrected VSD patients revealed increased airway resistance in the small airways, 30 ± 22% versus 15 ± 14% of total resistance, p <0.01, and reduced diffusion capacity, 84 ± 12% versus 101 ± 11%, p <0.01. Patients with a small, unrepaired VSD had comparable pulmonary function to their matched controls. In conclusion, VSD patients 40 years of age or older demonstrated significant impaired pulmonary function in terms of reduced dynamic pulmonary function, increased airway resistance in the small airways, and reduced diffusion capacity up to 54 years after defect closure compared with healthy age- and gender-matched controls.

Disappearance of the shunt and lower cardiac index during exercise in small, unrepaired ventricular septal defects

OBJECTIVES

Clinical studies have revealed decreased exercise capacity in adults with small, unrepaired ventricular septal defects. Increasing shunt ratio and growing incompetence of the aortic and pulmonary valve with retrograde flow during exercise have been proposed as reasons for the previously found reduced exercise parameters. With MRI, haemodynamic shunt properties were measured during exercise in ventricular septal defects.

METHODS

Patients with small, unrepaired ventricular septal defects and healthy peers were examined with MRI during exercise. Quantitative flow scans measured blood flow through ascending aorta and pulmonary artery. Scans were analysed post hoc where cardiac index, retrograde flows, and shunt ratio were determined.

RESULTS

In total, 32 patients (26 ± 6 years) and 28 controls (27 ± 5 years) were included. The shunt ratio was 1.2 ± 0.2 at rest and decreased to 1.0 ± 0.2 at peak exercise, p < 0.01. Aortic cardiac index was lower at peak exercise in patients (7.5 ± 2 L/minute/m2) compared with controls (9.0±2L l/minute/m2), p<0.01. Aortic and pulmonary retrograde flow was larger in patients during exercise, p < 0.01. Positive correlation was demonstrated between aortic cardiac index at peak exercise and previously established exercise capacity for all patients (r = 0.5, p < 0.01).

CONCLUSIONS

Small, unrepaired ventricular septal defects revealed declining shunt ratio with increasing exercise and lower aortic cardiac index. Patients demonstrated larger retrograde flow both through the pulmonary artery and the aorta during exercise compared with controls. In conclusion, adults with unrepaired ventricular septal defects redistribute blood flow during exercise probably secondary to a more fixed pulmonary vascular resistance compared with age-matched peers.

Biventricular morphology in adults born with a ventricular septal defect

Ventricular septal defects - large, surgically closed or small, untreated - have demonstrated lower peak exercise capacity compared with healthy controls. The mechanisms behind these findings are not yet fully understood. Therefore, we evaluated biventricular morphology in adults with a ventricular septal defect using MRI. Adults with either childhood surgically closed or small, untreated ventricular septal defects and healthy controls underwent cine MRI for the evaluation of biventricular volumes and quantitative flow scans for measurement of stroke index. Scans were analysed post hoc in a blinded manner. In total, 20 operated patients (22±2 years) and 20 healthy controls (23±2 years) were included, along with 32 patients with small, unrepaired ventricular septal defects (26±6 years) and 28 controls (27±5 years). Operated patients demonstrated larger right ventricular end-diastolic volume index (103±20 ml/m2) compared with their controls (88±16 ml/m2), p=0.01. Heart rate and right ventricular stroke index did not differ between operated patients and controls. Patients with unrepaired ventricular septal defects revealed larger right ventricular end-diastolic volume index (105±17 ml/m2) compared with their controls (88±13 ml/m2), p<0.01. Furthermore, right ventricular stroke index was higher in unrepaired ventricular septal defects (53±12 ml/minute/m2) compared with controls (46±8 ml/minute/m2), p=0.02, with similar heart rates. Both patient groups' right ventricles were visually characterised by abundant coarse trabeculation. Positive correlations were demonstrated between right ventricular end-diastolic volume indices and peak exercise capacity in patients. Left ventricle measurements displayed no differences between groups. In conclusion, altered right ventricular morphology was demonstrated in adults 20 years after surgical ventricular septal defect repair and in adults with small, untreated ventricular septal defects.