To the Editor:

We thank Drs Zuin, Rigatelli, Roncon, and Zuliani for their thoughtful read of our manuscript. They correctly note that the right/left ventricular end-diastolic diameter ratio (RV/LV) is a simpler measurement and correlates with mortality in pulmonary embolism, and they speculate that it might be similarly applicable in sepsis. In the 2008 Fremont study, RV/LV was only 72% sensitive and 58% specific for mortality from pulmonary embolism.¹ The strongest predictors for mortality in that study were history of LV heart failure and hypotension, both over three times the odds of RV/LV. Possibly the mortality of pulmonary embolism is more attributable to shock than RV dysfunction, and perhaps the RV/LV is capturing some patients with low LV preload states rather than isolated RV enlargement. How much of the prognostic value in RV/LV in pulmonary embolism is attributable to the right ventricle vs the left ventricle is unclear, and it is less clear how this might be applicable to septic patients. Fortunately, the work of Cirulis et al² has already investigated the potential value of RV/LV in sepsis. In their detailed analysis of patients undergoing echocardiography in sepsis and septic shock, they found no correlation between RV/LV and mortality.

Characterization of the right ventricle, both in size and function, is a challenging endeavor. The RV/LV can be elevated in RV failure as well as in low LV preload. Although no measure is perfect, we favor characterizing RV function using markers that represent RV contractility. Tricuspid annulus systolic planar excursion, fractional area change, and longitudinal strain all capture information throughout the cardiac cycle, whereas RV/LV is assessed at end-diastole. Drs Zuin and colleagues correctly note the potential difficulty in assessing some of these measures. When image quality is too poor to delineate the endocardial border, the RV basal diameter measurement would similarly be impaired. Many of the factors that adversely affect the assessment of fractional area change and tricuspid annulus systolic planar excursion, such as obscuration of the free wall, cardiac translation, and non-orthogonal imaging, can similarly adversely affect RV basal diameter measurement. As more sophisticated echocardiographic assessments such as ventricular strain and three-dimensional echocardiography are increasingly implemented in the ICU, it seems we soon might better characterize RV dysfunction and its effects on septic patients.