SCMR 22nd Annual Scientific Sessions
Pressure-volume (PV) loops provides a wealth of clinically important information on cardiac function. Cardiovascular magnetic resonance (CMR) is the gold standard for measuring cardiac volumes, but only invasive measures can quantify pressure. Since invasive pressure measurements carry risk for the patient, PV-loops are not readily available in clinical routine or in clinical trials. Therefore, this study aimed to develop and validate a novel model-based technique for computing individualized non-invasive PV-loops.
The method is based on a model of the time-varying elastance. Input was non-invasive cuff pressure, and a left ventricular (LV) volume curve delineated from CMR images. The expected range of the end-diastolic pressure needs to be estimated by the user.
Fourteen pig experiments were included for validation (n=9) and training (n=5) purposes. All pigs in the validation set underwent CMR, cuff pressure in the tail, and LV pressure catheterization. Two pigs were examined seven days after induced myocardial infarction, and the remaining pigs were healthy.
Model parameters were optimized from the training set, using PV-transducer measurements. Validation was performed by comparing the calculated hemodynamic parameters stroke work, mechanical potential energy, and ventricular efficiency (Figure 1A) from in-vivo measured and model derived PV-loops. Furthermore, as a proof-of-concept, the model was applied to healthy controls (n=13) and heart failure patients (n=28) who underwent CMR and brachial cuff pressure.
A model calculated PV-loop is shown with its corresponding in vivo measured data in (Figure 1B). There was a strong agreement between in vivo and model calculated stroke work, mechanical potential energy, and ventricular efficiency (Figure 2). The model yielded lower efficiency in patients compared to controls, and a higher potential energy (Figure 3). Furthermore, the model produced realistic stroke work values, and physiologically representative PV-loops for controls and patients (Figure 1C).
This novel technique for is the first validated, non-invasive method to derive individualized LV PV-loops and associated quantitative measures, for potential use in the clinic or in clinical trials. Experimental validation showed a strong agreement between model output and in vivo derived measurements. Application in controls and heart failure patients yielded expected cohort differences.