New Formulae for Calculating Left Heart Pressure in Pulmonary Artery Hypertension Patients at the Bedside - Pages 17-25

Kenneth J. Warring-Davies

University of Huudersfield School of Human and Health Sciences in the Department of Behavorial Sciences Queengate Huddersfield HD1 3DH UK



Objective: To compare new empirical formulae in HeartSmart, to calculate the mean pulmonary artery and mean pulmonary artery occlusion (wedge) pressures to that of the Pulmonary Artery Catheter Thermodilution Method.

Method: 20 adult patients with pulmonary artery hypertension admitted on to Bradford Royal Infirmary NHS Trust Hospital UK Intensive Care Unit, where haemodynamic monitoring is routinely performed as part of the treatment using the thermodilution method compared to the HeartSmart to guide interventional fluid resuscitation etc. Each subject has six paired values of each left heart pressure and cardiac indexes to test the robustness of HeartSmart against the perceived ‘gold standard’ thermodilution method. This was a double blind study the haemodynamic variables of each technology were close enough to each other.

Results: Bland-Altman plot comparing the measured mean pulmonary artery pressure (MPAP) mmHg to the Heartsmart calculated pulmonary artery pressures (CPAP) mmHg: For mean of the differences between MPAP mmHg and CPAP mmHg = – 1.08 mmHg, Legend 1.

Comparing the measured mean pulmonary artery occlusion (wedge) pressure (MPWP) mmHg to the HeartSmart calculated pulmonary artery occlusion (wedge) pressure (CPWP) mmHg: For mean of the differences between MPWP mmHg and CPWP mmHg = – 0.56 mmHg, Legend 2.

Comparing the measured mean cardiac index in litres/min/m2 MCI to the HeartSmart calculated mean cardiac index in litres/min/m2 CCI: For mean of the differences between MCI litres/min/m2 and CCI litres/min/m2 = -0.03 litres/min/m2; Legend 5.

Conclusion: The results demonstrate HeartSmartTM software compares favourably with the Pulmonary Artery Catheter thermodilution method at the bedside and could be used interchangeably or replace PACTD.

Background: The incidence of pulmonary artery hypetension is on the increase in the United Kingdom. Primary pulmonary arterial hypertension is a rare disease that is characterized by increased pulmonary-artery pressure in the absence of common secondary causes of pulmonary hypertension, such as viruses auto immune system, chronic heart, lung, or thromboembolic disease. Before the advent of new and some novel therapies, patients with idiopathic or familial pulmonary arterial hypertension average survival rates were less than 7 years. Despite the progress in diagnostic techniques and treatment, pulmonary arterial hypertension is becoming more common although remaining a progressive, debilitating fatal disease. The clinical signs and symptoms can be nonspecific, patients often receive a diagnosis too late as the condition advances, deteriorates and of course treatment is less effective.

The use of the (PAC) right heart floatation pulmonary artery catheter (Swan-Ganz) to measure the mean pulmonary artery and mean pulmonary artery occlusion (capillary wedge) pressures is one means of confirming the diagnosis of pulmonary artery hypertension, although its use is not appropriate in neonates or paediatric cases.

Keywords: Empirical physiological formulae, left heart pressures, haemodynamics, pulmonary artery hypertension.