My video is better than yours: a new chapter for perioperative assessment of function?

Pulmonary valve implantation, Tetralogy of Fallot

Rozzi et al. [1] present an update on the novel method of acute intraoperative assessment of right ventricular function before and after pulmonary valve replacement (PVR) late after repair of tetralogy of Fallot. By placing a virtual marker on the surface of the heart they assess cardiac kinematic parameters immediately pre- and post-PVR: displacement, perimeter, contraction velocity, cardiac fatigue and energy expenditure. Exponential correlations, albeit with low coefficients, are made with right ventricular end-diastolic volume (RVEDV) index from preoperative magnetic resonance imaging (MRI) and a cut-off value of 147 ml/m² is found to predict immediate functional recovery. Based on this the study population, n = 12 was divided into 2 groups. All parameters improved after PVR; however, the recovery in group 2 was less predictable. The authors recommend an earlier timing of PVR, specifically a lowering of the preoperative RVEDV index threshold.

Some 30 years ago, as a final year medical student, I remember a particular conversation with my future surgical boss around the effects of a transannular patch after tetralogy of Fallot repair. I was surprised to hear the pulmonary insufficiency can be tolerated well and no further intervention may be required.

Our knowledge of detrimental effects of pulmonary regurgitation on right ventricular function and remodelling has evolved since those days. Cardiac MRI contributed to a great degree in helping to identify parameters, defining optimal timing of pulmonary valve implantation [2]. In combination with postoperative cardiac MRI at various intervals, we have a good understanding of immediate- and mid-term changes in indices of right ventricular function [3]. It is generally accepted that the cut-off limits for RVEDV and right ventricular end-systolic volume (RVESV) predicting right ventricular volume and function normalization are somewhere around 150–160 and 80–90 ml/m². This experimental study is unique in providing us with non-invasive insight into acute changes observed during PVR for tetralogy of Fallot and pulmonary insufficiency. The question is how is this going to narrow down indication criteria for PVR?

There are limitation to the current study and they should be subject of further research.

The methodology relies on perioperative variables such as volume load (the right ventricle being extremely sensitive to this) heart rate, rhythm and ventilation parameters. These are likely to change acutely during surgery, a fact that is also recognized by the authors.

Cardiopulmonary bypass and cross-clamp will also have variable effect on ventricular function and indeed 3 out of 12 patients required cross-clamp and 2 required inotropic support postoperatively. Both a likely to skew the results given the small study sample.

It is the RVESV index (less volume load dependent) that is a better marker of myocardial function and its recovery continues beyond the immediate postoperative period into midterm. Interestingly, the relationship of kinematic parameters with RVESV index is not presented. Let us not forget also that a validated assessment of function can be made by tissue Doppler echocardiography or ventricular strain. These are good surrogates of contractility, which can be available in the operating room and are well codified [4]. Ultimately, further understanding of the value of this experimental method will be gained by correlation of such data with other functional methods and postoperative mid-term cardiac MRI in a larger patient cohort.

Would I change my practice and implant a pulmonary valve using right ventricular volume indices as recommended by Rozzi et al.? Not yet, although we gained a better understanding of acute changes accompanying these procedures and I look forward to future developments. A combination of factors with symptoms, RVESV and RVEDV, right ventricular ejection fraction and regurgitant fraction together with objective data obtained during cardiopulmonary exercise testing will continue to determine timing of replacement of pulmonary valve in patient with chronic pulmonary valve incompetence.