Utility of the PAPi for Risk Stratification in the Setting of Acute Inferior Wall Myocardial Infarction

The presence of RV dysfunction increases the risk of cardiogenic shock, high-grade AV-conduction block, and in-hospital mortality.¹ A major cause of morbidity and mortality in acute inferior wall myocardial infarction (IWMI) can be attributed to right ventricular (RV) dysfunction. Early detection may help improve clinical outcomes in patients with RV dysfunction in the setting of acute IWMI.

Risk stratification using hemodynamic measurement tools is a necessary step toward optimizing patient care. The pulmonary artery pulsatility index (PAPi) is one such tool (calculated as the [(systolic pulmonary artery pressure – diastolic pulmonary artery pressure)/central venous pressure]). In patients in cardiogenic shock, this hemodynamic measurement index helps predict severe RV dysfunction during acute IWMI and aims to identify subjects requiring a percutaneous RV assist device (RVAD).

A retrospective study by Korabathina, et.al. examined the medical records of acute IWMI patients undergoing emergent PCI (n = 180) between 2008 and 2010.² Only 20 patients met the inclusion criteria and were ultimately included in the final analysis. Patients suspected of having a RVD received serial electrocardiograms, intra-aortic balloon pump, and pharmacological therapy, as needed. Medications utilized in this patient population included glycoprotein IIb/IIIa receptor inhibitors, aspirin, and anticoagulants.

Researchers defined two groups for comparison: 1) patients with nonobstructive coronary artery disease ([non-CAD], n = 50), and 2) patients presenting with acute coronary syndrome requiring left coronary stenting ([ACS], n = 14).

Compared to the non-CAD the ACS group had a lower PAPi in suspected RV dysfunction (5.52 ± 4.40 vs 4.32 ± 3.04 vs 1.11 ± 0.57, respectively, P < 0.01). RV stroke work in participants with suspected RV dysfunction compared with controls (9.50 ± 8.01 vs 17.71 ± 12.24 vs 17.53 ± 10.32, respectively, P < 0.05). The PAPi showed the strongest association with estimates of RV systolic function compared with the other hemodynamic variables studied (r = -0.731, P < 0.001).

Subjects were also grouped according to clinical outcomes: 1) the need for a percutaneous RV support device (pRVSD), 2) in-hospital mortality, and 3) in-hospital mortality plus the need for any pRVSD. A decreased PAPi was consistently found among subjects with the combined outcome of in-hospital death and/or need for a pRVSD.

According to the authors, the PAPi showed the highest specificity (98.3%) and the highest sensitivity (88.9%) in the prediction of in-hospital mortality when compared to the RA:PCWP ratio and the RVSW.  The PAPi also demonstrated specificity and sensitivity for predicting the need of a pRVSD with a diagnostic accuracy of 97.1%.

Hemodynamic measurements using the PAPi may provide accurate identification of patients with severe RV dysfunction and predict the need for advanced mechanical support. A receiver-operating characteristic curve analysis determined an optimal cut-point value for the PAPi of ≤0.9, with the PAPi providing 98.3% specificity and 100.0% sensitivity for the prediction of in-hospital mortality.

PAPi and RVSW values were analyzed prior to implantation and following explantation of the pRVSD to evaluate the effects of the device on hemodynamics after acute IWMI. Following explantation, there was significant hemodynamic improvement according to PAPi (0.53 ± 0.21 vs 1.10 ± 0.40, P < 0.01) and RVSW (4.06 ± 3.53 vs 12.16 ± 5.30, P < 0.01) values.

The use of invasive hemodynamic measurements with the PAPi may identify patients with severe RV dysfunction while acting as a risk stratification and prediction tool for in-hospital mortality and the need for mechanical circulatory support.

Limitations to this study included the strict inclusion criteria and the subsequent small number of patients (n = 20) enrolled in the final analysis. To arrive at a stronger conclusion, further studies regarding the prognostic capability of the PAPi for patients requiring pRVSD in significantly larger patient populations are needed.