Quantitative MRI comparison of systemic hemodynamics in Mustard/Senning repaired patients and healthy volunteers at rest

The future of adult patients after Mustard or Senning repair for transposition of the great arteries

BACKGROUND

After Mustard or Senning repair for transposition of the great arteries (d-TGA), qualitative assessment of the systemic right ventricle remains difficult. We wanted to evaluate the relationship between demographic and echocardiographic variables, and exercise performance.

METHODS

In 22 consecutive d-TGA patients (9 Mustard and 13 Senning) a standard transthoracic echocardiogram was performed. Peak oxygen consumption (peak VO2, ml/kg/min) was obtained by a bicycle stress test. Cardiac index (CI) at rest, 50 W, and 100 W was calculated from cardiac output, obtained by CO2 rebreathing.

RESULTS

The group of patients consisted in 15 male and 7 female with a median age of 21 (range 17-34) years. On echocardiographic evaluation, right ventricular function was normal in one, slightly impaired in 11, moderately impaired in 9, and severely impaired in one. Peak VO2 was 27.4+/-7.9 ml/kg/min, which was 64+/-16% of predicted values in normals. CI at rest, 50 Watt, and 100 Watt, were 2.7+/-0.5, 5.6+/-1.2, and 6.8+/-1.1 l/min/m2, respectively. No relationship between echocardiographic parameters and exercise capacity was found. Age correlated significantly with CI at 50 and 100 W (rho=-0.44, P=0.045 and rho=-0.77, P=0.0001, respectively). Finally, simple regression analysis identified a linear relationship between age and CI at 100 W (bèta=-0.54 and R2=0.29, P=0.014).

CONCLUSIONS

Maximal exercise capacity is reduced in adult patients after Mustard or Senning repair. Standard echocardiographic 2D-measurements are insufficient to determine the reduction in their functional capacity. The inverse relationship between age and the cardiac indices suggests an age dependent and progressive diminution of systemic ventricular function.

Quantitative MRI comparison of pulmonary hemodynamics in mustard/senning-repaired patients suffering from transposition of the great arteries and healthy volunteers at rest

In Mustard/Senning-repaired (MSR) patients, the right and left ventricles (RV, LV) act as the systemic and pulmonary ventricle, respectively. The purpose of the study was to compare non-invasively, at rest, pulmonary ventricle systolic function and hemodynamics in MSR patients with those of healthy volunteers. Velocity-encoded MR imaging was performed at the level of the main pulmonary artery (MPA) in ten male patients late after a Mustard/Senning correction performed early in infancy and in ten male volunteers. Both blood flow and MPA cross-sectional area variations were recorded over a complete cardiac cycle. MPA distensibility, body surface area (BSA)-normalized pulmonary ventricle systolic power and work were significantly lower in the MSR patients compared to volunteers. In particular, BSA-normalized LV systolic power and work in MSR patients were equal to 82 and 77% on average of those of the RV in volunteers (0.32 vs. 0.39 W/m2 and 0.10 vs. 0.13 J/m2), respectively. We conclude that in MSR patients at rest two unrelated findings were observed: (1) a reduced MPA distensibility and (2) a significantly lower systolic mechanical performance of the pulmonary LV compared to that of the RV in healthy volunteers. The latter quantification indirectly confirms the lowest systemic RV systolic mechanical performance previously published.

Applications of phase-contrast flow and velocity imaging in cardiovascular MRI

A review of cardiovascular clinical and research applications of MRI phase-contrast velocity imaging, also known as velocity mapping or flow imaging. Phase-contrast basic principles, advantages, limitations, common pitfalls and artefacts are described. It can measure many different aspects of the complicated blood flow in the heart and vessels: volume flow (cardiac output, shunt, valve regurgitation), peak blood velocity (for stenosis), patterns and timings of velocity waveforms and flow distributions within heart chambers (abnormal ventricular function) and vessels (pulse-wave velocity, vessel wall disease). The review includes phase-contrast applications in cardiac function, heart valves, congenital heart diseases, major blood vessels, coronary arteries and myocardial wall velocity.

Transposition of the great arteries: long-term outcome and current management

There is a large group of young adults who survived atrial baffle repair of transposition of the great arteries. Most survivors are asymptomatic, although nearly all have decreased exercise capacity. Loss of sinus rhythm and atrial arrhythmias are common and increase with age. There is concern about the ability of the right ventricle to function long term as a systemic pump, and recent publications have highlighted right ventricular dysfunction in this patient population. Sudden death and congestive heart failure are the main causes of death, and outcomes beyond 30 years are unknown. Pulmonary artery banding, late arterial switch, and cardiac transplantation are employed when intractable arrhythmias or right ventricular failure threaten survival or quality of life.