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Derivation of Indices of Left Ventricular Contractility in the Setting of Continuous‐Flow Left Ventricular Assist Device Support
Author(s) -
Gupta Sunil,
Muthiah Kavitha,
Woldendorp Kei,
Robson Desiree,
Jansz Paul,
Hayward Christopher S.
Publication year - 2014
Publication title -
artificial organs
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.684
H-Index - 76
eISSN - 1525-1594
pISSN - 0160-564X
DOI - 10.1111/aor.12292
Subject(s) - ventricle , cardiology , contractility , medicine , diastole , systole , acceleration , mathematics , physics , blood pressure , classical mechanics
It is important to accurately monitor residual cardiac function in patients under long‐term continuous‐flow left ventricular assist device ( cfLVAD ) support. Two new measures of left ventricular ( LV ) chamber contractility in the cfLVAD ‐unloaded ventricle include I Q , a regression coefficient between maximum flow acceleration and flow pulsatility at different pump speeds; and K , a logarithmic relationship between volumes moved in systole and diastole. We sought to optimize these indices. We also propose RI Q , a ratio between maximum flow acceleration and flow pulsatility at baseline pump speed, as an alternative to I Q . Eleven patients (mean age 49 ± 11 years) were studied. The K index was derived at baseline pump speed by defining systolic and diastolic onset as time points at which maximum and minimum volumes move through the pump. I Q across the full range of pump speeds was markedly different between patients. It was unreliable in three patients with underlying atrial fibrillation (coefficient of determination R 2 range: 0.38–0.74) and also when calculated without pump speed manipulation ( R 2 range: 0.01–0.74). The K index was within physiological ranges, but poorly correlated to both I Q ( P = 0.42) and RI Q ( P = 0.92). In four patients there was excellent correspondence between RI Q and I Q , while four other patients showed a poor relationship between these indices. As RI Q does not require pump speed changes, it may be a more clinically appropriate measure. Further studies are required to determine the validity of these indices.