Normalization of Right Ventricular Performance and Remodeling Evaluated by Magnetic Resonance Imaging at Late Follow-up of Heart Transplantation: Relationship Between Function, Exercise Capacity and Pulmonary Vascular Resistance

Right ventricular hemodynamics and performance in relation to perfusion during first year after heart transplantation

Aims

We aim to evaluate changes in invasive haemodynamics, right ventricular (RV) function, and perfusion during the first year after heart transplantation (HTx) and to determine the relation between RV function and myocardial perfusion.

Methods and results

Thirty patients were prospectively enrolled at the time of HTx. Right heart catheterization (RHC), comprehensive 2D and 3D echocardiography and cardiac biomarkers were performed at baseline (≤2 weeks after HTx) and at follow‐up 1, 3, 6, and 12 months after HTx. At 12 months, HTx patients were subjected to an exercise stress test with assessment of maximal oxygen consumption (VO₂max). RV myocardial perfusion reserve was evaluated by ¹⁵O‐H₂O positron emission tomography at baseline and at 3 and 12 months after HTx. A group of 43 healthy subjects served as echocardiographic controls and a subgroup comprising 16 healthy controls underwent exercise stress test with simultaneous RHC. At baseline, HTx patients had higher pulmonary artery wedge pressure (PAWP) and right atrial pressure (RAP) and pulmonary vascular resistance (PVR) than healthy controls whereas cardiac index (CI) was reduced (PAWP; 14 mmHg [8;17] vs. 8 mmHg [7;10]; RAP: 7 mmHg [4;11] vs. 5 mmHg [4;6]; PVR: 1.9 wood units [1.3;2.6] vs. 1.1 wood units [1.0;1.4]; CI 2.4 L/min/m² [2.2;2.8] vs. 3.3 L/min/m² [2.8;.3.6], all P < 0.05). Normalization of filling pressures and CI was seen 3–6 months after HTx. During follow‐up, RV function in terms of 3D ejection fraction (EF) and longitudinal strain (LS) improved in HTx patients but remained reduced compared with healthy controls at 12 months follow‐up (3D RV EF: 52 ± 7% vs. 60 ± 8%; RV LS: 22 ± 4% vs. 28 ± 5%, both P < 0.001). During follow‐up, RV perfusion reserve improved (baseline 2.1 ± 0.9; 3 months follow‐up 3.2 ± 0.8; 12 months follow‐up 3.7 ± 1.1, P < 0.0001). RV perfusion reserve significantly correlated to cardiac markers in terms of troponin T (r = −0.62, P < 0.0001), NT‐proBNP (r = −0.65, P < 0.0001), RAP (r = −0.43, P < 0.01) and CI (r = 0.37, P < 0.01) and with VO₂max 12 months after HTx (r = 0.75, P < 0.01).

Conclusions

Normalization of left and right atrial filling pressures is demonstrated within the first 3 to 6 months after HTx. RV function and RV perfusion reserve correlated and gradually improved during the first year after HTx but RV function remained reduced in HTx patients compared with healthy controls.

Dominance of free wall radial motion in global right ventricular function of heart transplant recipients

Assessment of right ventricular (RV) function using conventional echocardiography might be inadequate as the radial motion of the RV free wall is often neglected. Our aim was to quantify the longitudinal and the radial components of RV function using three-dimensional (3D) echocardiography in heart transplant (HTX) recipients. Fifty-one HTX patients in stable cardiovascular condition without history of relevant rejection episode or chronic allograft vasculopathy and 30 healthy volunteers were enrolled. RV end-diastolic (EDV) volume and total ejection fraction (TEF) were measured by 3D echocardiography. Furthermore, we quantified longitudinal (LEF) and radial ejection fraction (REF) by decomposing the motion of the RV using the ReVISION method. RV EDV did not differ between groups (HTX vs control; 96 ± 27 vs 97 ± 2 mL). In HTX patients, TEF was lower, however, tricuspid annular plane systolic excursion (TAPSE) decreased to a greater extent (TEF: 47 ± 7 vs 54 ± 4% [-13%], TAPSE: 11 ± 5 vs 21 ± 4 mm [-48%], P < .0001). In HTX patients, REF/TEF ratio was significantly higher compared to LEF/TEF (REF/TEF vs LEF/TEF: 0.58 ± 0.10 vs 0.27 ± 0.08, P < .0001), while in controls the REF/TEF and LEF/TEF ratio was similar (0.45 ± 0.07 vs 0.47 ± 0.07). Current results confirm the superiority of radial motion in determining RV function in HTX patients. Parameters incorporating the radial motion are recommended to assess RV function in HTX recipients.

Three-Dimensional Right Ventricular Strain Versus Volume Quantification in Heart Transplant Recipients in Relation to Pulmonary Artery Pressure

OBJECTIVES

Residual pulmonary hypertension challenges the right ventricular function and worsens the prognosis in heart transplant recipients. The complex geometry of the right ventricle complicates estimation of its function with conventional transthoracic echocardiography. We evaluated right ventricular function in heart transplant recipients with the use of 3-dimensional echocardiography in relation to systolic pulmonary artery pressure.

MATERIALS AND METHODS

We performed 32 studies in 26 heart transplant patients, with 6 patients having 2 studies at different time points with different pressures and thus included. Right atrial volume, tricuspid annular plane systolic excursion, peak systolic annular velocity, fractional area change, and 2-dimensional speckle tracking longitudinal strain were obtained by 2-dimensional and tissue Doppler imaging. Three-dimensional right ventricular volumes, ejection fraction, and 3-dimensional right ventricular strain were obtained from the 3-dimensional data set by echocardiographers. Systolic pulmonary artery pressure was obtained during right heart catheterization.

RESULTS

Overall mean systolic pulmonary artery pressure was 26 ± 7 mm Hg (range, 14-44 mmHg). Three-dimensional end-diastolic (r = 0.75; P < .001) and end-systolic volumes (r = 0.55; P = .001)correlated well with systolic pulmonary artery pressure. Right ventricular ejection fraction and right atrium volume also significantly correlated with systolic pulmonary artery pressure (r = 0.49 and P = .01 for both). However, right ventricular 2- and 3-dimensional strain, tricuspid annular plane systolic excursion, and tricuspid annular velocity did not.

CONCLUSIONS

The effects of pulmonary hemodynamic burden on right ventricular function are better estimated by a 3-dimensional volume evaluation than with 3-dimensional longitudinal strain and other 2-dimensional and tissue Doppler measurements. These results suggest that the peculiar anatomy of the right ventricle necessitates 3-dimensional volume quantification in heart transplant recipients in relation to residual pulmonary hypertension.

Exercise limitation following transplantation

Organ transplantation is one of the medical miracles or the 20th century. It has the capacity to substantially improve exercise performance and quality of life in patients who are severely limited with chronic organ failure. We focus on the most commonly performed solid-organ transplants and describe peak exercise performance following recovery from transplantation. Across all of the common transplants, evaluated significant reduction in VO2peak is seen (typically renal and liver 65%-80% with heart and/or lung 50%-60% of predicted). Those with the lowest VO2peak pretransplant have the lowest VO2peak posttransplant. Overall very few patients have a VO2peak in the normal range. Investigation of the cause of the reduction of VO2peak has identified many factors pre- and posttransplant that may contribute. These include organ-specific factors in the otherwise well-functioning allograft (e.g., chronotropic incompetence in heart transplantation) as well as allograft dysfunction itself (e.g., chronic lung allograft dysfunction). However, looking across all transplants, a pattern emerges. A low muscle mass with qualitative change in large exercising skeletal muscle groups is seen pretransplant. Many factor posttransplant aggravate these changes or prevent them recovering, especially calcineurin antagonist drugs which are key immunosuppressing agents. This results in the reduction of VO2peak despite restoration of near normal function of the initially failing organ system. As such organ transplantation has provided an experiment of nature that has focused our attention on an important confounder of chronic organ failure-skeletal muscle dysfunction.

Total Ischemia Time Alters the Longitudinal and Circumferential Shortening of the Right Ventricle in Transplanted Hearts

Objectives. Ischemia time is a risk factor for mortality and right ventricular (RV) failure after heart transplantation. The purpose of this study was to determine the effect of ischemia time on known transesophageal echocardiography (TEE) parameters of RV function and on a novel quantitative measurement of RV circumferential shortening. Methods. Right and left ventricular (LV) function was evaluated retrospectively in 20 consecutive patients after heart transplant using known TEE parameters as well as a quantitative measurement of circumferential contraction. The control group consisted of 20 patients undergoing coronary artery bypass grafting (CABG) with no documented RV dysfunction. Results. Posttransplant TEE parameters of RV function were depressed compared with post–cardiopulmonary bypass CABG patients. Significant correlation was observed between tricuspid annular planar systolic excursion, basal, mid, and global circumferential shortening and total ischemia time. Conclusion. Total ischemia time of the transplanted heart may play a role in deterioration of longitudinal and circumferential shortening of the RV.

Electrical modalities beyond pacing for the treatment of heart failure

In this review, we report on electrical modalities, which do not fit the definition of pacemaker, but increase cardiac performance either by direct application to the heart (e.g., post-extrasystolic potentiation or non-excitatory stimulation) or indirectly through activation of the nervous system (e.g., vagal or sympathetic activation). The physiological background of the possible mechanisms of these electrical modalities and their potential application to treat heart failure are discussed.

Combined heart-kidney transplantation: a review of recipient selection and patient outcomes

Elevated serum creatinine is a common finding among patients awaiting heart transplantation because of reduced renal perfusion in the setting of severe heart failure as well as overlapping risk factors for chronic kidney disease and heart disease. Patients with significant renal dysfunction preoperatively have worse outcomes with heart transplantation alone compared with those with normal renal function or those with renal dysfunction who undergo combined heart-kidney transplantation. Optimizing organ distribution and patient outcomes after cardiac transplantation requires appropriate recipient selection, including deciding which patients will benefit from combined heart-kidney transplantation. This review focuses on the evaluation of patients with chronic kidney disease awaiting heart transplantation and the outcomes of combined heart-kidney transplantation.