Journal of the Practice of Cardiovascular Sciences

CURRICULUM IN CARDIOLOGY - JOURNAL CLUB
Year
: 2019  |  Volume : 5  |  Issue : 2  |  Page : 105--107

Ventricular-arterial coupling: A novel echocardiographic risk factor for pediatric dilated cardiomyopathy


Sakshi Sachdeva 
 Department of Cardiology, Cardio Neuro Centre, All Institute of Medical Sciences, New Delhi, India

Correspondence Address:
Dr. Sakshi Sachdeva
Department of Cardiology, Cardio Neuro Centre, All India Institute of Medical Sciences, 7th Floor, Ansari Nagar, New Delhi - 110 029
India

Abstract

Ventricular-arterial coupling, earlier used for research and experimental purposes, is being used currently for bedside patient evaluation and decision making. Its use in adults with heart failure has been proven. In pediatric heart failure, due to dilated cardiomyopathy, its use as a prognostic tool has been first documented in this study, and cutoff values determining outcome, have been derived.



How to cite this article:
Sachdeva S. Ventricular-arterial coupling: A novel echocardiographic risk factor for pediatric dilated cardiomyopathy.J Pract Cardiovasc Sci 2019;5:105-107


How to cite this URL:
Sachdeva S. Ventricular-arterial coupling: A novel echocardiographic risk factor for pediatric dilated cardiomyopathy. J Pract Cardiovasc Sci [serial online] 2019 [cited 2021 Sep 24 ];5:105-107
Available from: https://www.j-pcs.org/text.asp?2019/5/2/105/264628


Full Text



 Citation



Capone CA, Lamour JM, Lorenzo J, Tria B, Ye K, Hsu DT, et al. Ventricular-arterial coupling: A novel echocardiographic risk factor for disease progression in pediatric dilated cardiomyopathies (DCMs). Pediatric Cardiol 2019;40:330-8.

 Background



Coupling is a term commonly used in mechanical engineering. Coupling between two systems depends on how efficient is the energy transfer from one to another, without much losses in overcoming resistance. In cardiovascular system, it pertains to energy transfer from ventricle to systemic arterial circulation, for maintenance of organ perfusion, commonly called as ventricular arterial (VA) coupling (ventricular-arterial coupling).[1] Best coupled systems, theoretically, have 100% energy transfer, without any loss, i.e., coupling ratio 1. But, in practice, VA coupling in adults in resting state varies from 0.6 to 1.2.

Mathematically, Ventricular-arterial coupling is measured by the ratio of arterial elastance (Ea) to left ventricular (LV) end-systolic elastance (Ees) (VA coupling = Ea/Ees). It is a measure of the interaction between myocardial performance and vascular function. When measured invasively, it is a reliable and effective index of cardiovascular performance, reflecting the adequate transmission of stroke volume to peripheral circulation at the lowest possible energy consumption. It gets impaired in heart failure, and echocardiographic VA coupling has been used for disease progression and prognostication in adults.

LV Ees is represented by the slope of the end-systolic pressure-end-systolic volume relationship. It is a load-independent measure of myocardial contractility and stiffness. Normal range in humans is 2.3 ± 1 mm Hg/ml. Ea is represented by the slope of the end-systolic pressure-end diastolic volume relationship. It is a measure of total afterload on the left ventricle. Normal range in humans is 2.2 ± 0.8 mm Hg/ml.[2]

Echocardiographic LV elastance (Ees) is calculated as (0.9 × systolic blood pressure) ÷ (2D echocardiographic end-systolic volume). Echocardiographic Ea is calculated as, (0.9 × systolic blood pressure) ÷ (2-D echocardiographic stroke volume). VA coupling (Ea: Ees) is calculated as 2D echo derived end-systolic volume/stroke volume.[3] The derivation of VA coupling in a case example is depicted in [Figure 1].{Figure 1}

Capone et al. undertook the study to determine if VA coupling is different in pediatric patients with DCM compared to normal controls and to determine if VA coupling is different in pediatric DCM patients with poor outcome compared to those without. It is first of its kind study in pediatric DCMP.

 Methods



It was a retrospective, cohort study including pediatric patients (0–21 years), who presented to Children's Hospital at Montefiore, from January 2008 to January 2017, with DCM. DCM was defined as left ventricular end-diastolic dimension Z score >2, and LV ejection fraction (EF) <50%. Exclusion criteria were patients with congenital heart disease, on mechanical circulatory support (MCS), listed for transplant at the time of presentation, or with the first presentation after 2015. 48 patients and 97 age- and gender-matched controls were analyzed, and outcomes studied at 2 years after entry to the cohort. Data were extracted from medical records. Poor outcome was defined as composite outcome of MCS, death, or transplant.

 Results



Mean age at presentation was 9 ± 7 years, 48% (n = 23) patients were in NYHF/Ross Class II-III, and 52% (n = 25) patients were in NYHF/Ross Class IV. Patients with DCM had significantly higher heart rate, lower blood pressure, higher LV dimensions, lower EF, and poor tissue Doppler indices, compared to age- and gender-matched normal controls. Ea was significantly higher, and ventricular Ees was significantly lower in DCM group. VA coupling derived from the ratio of Ea and ventricular Ees was significantly higher in DCM group.

Twenty-seven (56%) patients reached composite endpoint by the end of 2 years, 1 patient died and 26 patients underwent cardiac transplant. The comparison of the two DCM groups (with poor outcome and good outcome) revealed that patients with poor outcome were significantly younger, had acute heart failure, had worse NYHF/Ross class, and higher heart rates compared to the patients with good outcome. Echocardiographically, they had larger LV dimensions, worse LV EF, poor sphericity index, more severe mitral regurgitation (MR), and worse tissue Doppler velocities. They also had significantly higher Ea, lower ventricular elastance, and higher VA coupling ratio.

In multi-group analysis, VA coupling and LV elastance were significantly different in all three groups. Arterial elastance was higher in patients who had poor outcome, but no difference in control versus those with good DCM outcomes. Receiver operating characteristic curves showed that both VA coupling and EF were significantly associated with outcome as seen by area under the curve. CART risk stratification revealed that among all the variables, VA coupling ratio ≥2, was the top discriminator of poor outcome with no additional variables needed to stratify. Kaplan–Meier curve analysis demonstrated patients with VA coupling ratio ≥2 had significantly poor event-free survival.

 Discussion



Children with DCM have higher arterial elastance, lower ventricular elastance, and higher VA coupling ratio than age- and gender-matched controls. These parameters allowed discrimination between patients who required a transplant or died versus those who did not. Previously, a limited number of echocardiographic markers have been consistently acknowledged to help predict outcomes, namely EF, larger left ventricle end-diastolic M-mode dimension z-score, lower septal peak systolic tissue Doppler velocity z-score, and severity of MR.[4],[5],[6],[7]

VA coupling reflects the adequate transmission of stroke volume to peripheral circulation at the lowest possible energy consumption. It may be a reliable and effective index of cardiovascular performance. A higher VA coupling ratio is associated with worse outcome in pediatric patients with DCM. Normative values are not established in pediatric population. Further study of VA coupling, Ea, and LV elastance may offer a unique insight into the pathophysiology and treatment targeting specific mechanisms of heart failure in pediatric DCM.[8]

Limitations of the study include its retrospective nature, small sample size, varied presentation (acute vs. chronic) of the population, referral bias toward sicker patients, being referral center for transplant in the region. Limitations due to image quality and observer variability and inherent assumptions in noninvasive measurements of VA coupling were also present.

Weblink

https://drive.google.com/file/d/1YcFg_R6UOiyLO6jhCOB16t2nHCHIGJ69/view?usp=sharing

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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