A Novel Methodology to Measure Serial Changes in Left Ventricular Pressure in Ambulatory Canines After Heart Failure Induction and Neuromodulatory Therapy

Background A novel technique to measure hemodynamic function in ambulatory canines was used to quantify serial changes in left ventricular hemodynamic function after myocardial infarction (MI), pacing-induced heart failure (HF), and treatment with spinal cord stimulation (SCS). Methods Telemetric devices were implanted into 6 canines to continuously measure left ventricular pressure (LVP) in freely moving ambulatory canines. Data were collected for 1 day in each of the following stages: baseline (6 canines), 7 days after foam embolization of the left anterior descending artery to induce MI (4 canines), and 1 day after high-rate right ventricular pacing to induce HF (3 canines). Left ventricular end-diastolic pressure (LVEDP) and max positive and negative dP/dt were extracted from LVP waveforms for 10-minute intervals over each hour of the day to produce a daily mean. Left ventricular ejection fraction (LVEF) was also obtained using echocardiography at baseline and after HF. Results Results are presented in the table. LVEDP, +dP/dt, and –dP/dt were not significantly changed after MI. However, these parameters were significantly changed after HF. In 2 animals, 5 weeks of therapy with SCS restored +dP/dt (1780 mm Hg/s) and –dP/dt (–1666 mm Hg/s) to baseline levels. Tabled 1 Treatment P value Parameter Baseline MI HF Baseline to MI MI to HF Baseline to HF LVEDP (mm Hg) 5 ± 2 4 ± 4 25 ± 24 .671 .14 .067 +dP/dt (mm Hg/s) 1907 ± 202 1970 ± 314 1189 ± 294 .716 .021* .0033* -dP/dt (mm Hg/s) -1659 ± 97 -1708 ± 36 -1275 ± 286 .372 .027* .017* LVEF (%) 58 ± 5 — 22 ± 2 — — .00002* *Statistical significance indicated by P