Energy Costs of Singular and Concomitant Pressure and Volume Overload Lesions

The objective of this study is to propose a theoretical framework to utilize the ventricular power overhead rates of HT, aortic regurgitation (AR), aortic stenosis (AS), and mitral regurgitation (MR) as a new means to assess severity, particularly under concomitant conditions. A lumped parameter model was utilized to evaluate the ventricular energy budget under normal, singular, and concomitant combinations of HT, AS, AR, and MR; and calculate energy overhead rate defined as the % increase in ventricular power output. Disease severity for each lesion was modeled at mild, moderate, and severe levels per AHA/ACC guidelines. The overhead rate for HT and AS were 15% (mild), 25% (moderate), and 45% (severe); AR and MR corresponded to 40% (moderate) and 100% (severe). The overhead rate as a function of regurgitant fraction was shown to be highly nonlinear. The overhead rate for concomitant lesions were 39% (mild HT+mild AS), 51% (mild HT+mild AR), 46% (mild HT+mild MR), 51% (mild AS+mild AR), 37% (mild AS+mild MR), and 44% (mild AR+mild MR). Power overhead under volume overload increases nonlinearly while that for pressure overload is linear. Concomitant lesions involving pressure (and volume?) overload produce a net overhead rate greater than the sum of individual lesions. Synergy in overhead rates is most with the presence of uncontrolled HT.
Source: Cardiovascular Engineering and Technology - Category: Cardiology Source Type: research