Michael Poullis1. 1. Department of Cardiothoracic Surgery, Liverpool Heart and Chest Hospital, Liverpool, UK mpoullis@hotmail.com.
Abstract
OBJECTIVES: To determine the effect of differing modes of left ventricular assist device (LVAD) operation: synchronous, independent (asynchronous or pseudosynchronous) or counter pulsation (antisynchronous), on left atrial pressure, pulmonary artery pressure, pulmonary blood flow and right ventricular work load, utilizing a previously published electrical analogy of the systemic and pulmonary circulation and the heart. METHODS: A previously published electrical analogy of the systemic and pulmonary circulation was utilized. The Simulation Package with Integrated Circuit Emphasis (LTSPICE IV) was utilized. Three LVAD operation mode scenarios were analysed: synchronous, counter pulsation and independent pulsatile. The root mean square of the pulmonary artery pressure (PAP), left atrial pressure (LAP) and pulmonary blood flow (PBF) were calculated, as was the right ventricular work load. RESULTS: Counter pulsation LVAD operation resulted in the lowest LAP, PAP, right ventricular work load and the highest pulmonary blood flow. Independent pulsation resulted in the highest LAP, PAP and the lowest pulmonary blood flow. This technique actually increased RV work load. CONCLUSIONS: If an LVAD is to be operated in a pulsatile mode, the counter pulsation mode reduces pulmonary artery and left atrial pressure and increases pulmonary blood flow and thus cardiac output. This is in addition to the reduced right ventricular energetic requirement, a finding previously described. Clinical validation of our findings is necessary.
OBJECTIVES: To determine the effect of differing modes of left ventricular assist device (LVAD) operation: synchronous, independent (asynchronous or pseudosynchronous) or counter pulsation (antisynchronous), on left atrial pressure, pulmonary artery pressure, pulmonary blood flow and right ventricular work load, utilizing a previously published electrical analogy of the systemic and pulmonary circulation and the heart. METHODS: A previously published electrical analogy of the systemic and pulmonary circulation was utilized. The Simulation Package with Integrated Circuit Emphasis (LTSPICE IV) was utilized. Three LVAD operation mode scenarios were analysed: synchronous, counter pulsation and independent pulsatile. The root mean square of the pulmonary artery pressure (PAP), left atrial pressure (LAP) and pulmonary blood flow (PBF) were calculated, as was the right ventricular work load. RESULTS: Counter pulsation LVAD operation resulted in the lowest LAP, PAP, right ventricular work load and the highest pulmonary blood flow. Independent pulsation resulted in the highest LAP, PAP and the lowest pulmonary blood flow. This technique actually increased RV work load. CONCLUSIONS: If an LVAD is to be operated in a pulsatile mode, the counter pulsation mode reduces pulmonary artery and left atrial pressure and increases pulmonary blood flow and thus cardiac output. This is in addition to the reduced right ventricular energetic requirement, a finding previously described. Clinical validation of our findings is necessary.