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R A Bleasdale

Publications and source records attributed to R A Bleasdale.

7 recordsLinked to original sources
PubMed2004

Left ventricular pacing minimizes diastolic ventricular interaction, allowing improved preload-dependent systolic performance.

BACKGROUND: Left ventricular (LV) pacing improves hemodynamics in patients with heart failure. We hypothesized that at least part of this benefit occurs by minimization of external constraint to LV filling from ventricular interaction. METHODS AND RESULTS: We present median values (interquartile ranges) for 13 heart failure patients with LV pacing systems implanted for New York Heart Association class III/IV limitation. We used the conductance catheter method to measure LV pressure and volume simultaneously. External constraint was measured from the end-diastolic pressure-volume relation recorded during inferior vena caval occlusion, during LV pacing, and while pacing was suspended. External constraint to LV filling was reduced by 3.0 (4.6 to 0.6) mm Hg from 4.8 (0.6 to 7.5) mm Hg (P<0.01) in response to LV pacing; effective filling pressure (LV end-diastolic pressure minus external constraint) increased by 4.0 (2.2 to 5.8) mm Hg from 17.7 (13.3 to 22.6; P<0.01). LV end-diastolic volume increased by 10 (3 to 11) mL from 238 (169 to 295) mL (P=0.01), whereas LV end-systolic volume did not change significantly (-1 [-2 to 3] mL from 180 [124 to 236] mL, P=0.97), which resulted in an increase in stroke volume of 11 (5 to 13) mL from 49 (38 to 59) mL (P<0.01). LV stroke work increased by 720 (550 to 1180) mL . mm Hg from 3400 (2110 to 4480) mL . mm Hg (P=0.01), and maximum dP/dt increased by 120 (2 to 161) mm Hg/s from 635 (521 to 767) mm Hg/s (P=0.03). CONCLUSIONS: This study suggests a potentially important mechanism by which LV pacing may produce hemodynamic benefit. LV pacing minimizes external constraint to LV filling, resulting in an increase in effective filling pressure; the consequent increase in LV end-diastolic volume increases stroke volume via the Starling mechanism.

Aged↗
PubMed2004

Left ventricular pacing improves haemodynamic variables in patients with heart failure with a normal QRS duration.

OBJECTIVES: To assess whether patients with congestive heart failure (CHF) and a normal QRS duration can benefit from left ventricular (VDD-LV) pacing. DESIGN: Cardiac resynchronisation is reserved for patients with a broad QRS duration on the premise that systolic resynchronisation is the mechanism of benefit, yet improvement from pacing correlates poorly with QRS duration. In CHF patients with a broad QRS duration, those with a high resting pulmonary capillary wedge pressure (PCWP) > 15 mm Hg benefit. In this acute haemodynamic VDD-LV pacing study, patients with CHF with a normal QRS duration were divided into two groups--patients with a resting PCWP > 15 mm Hg and patients with a resting PCWP < 15 mm Hg--to determine whether benefit is predicted by a high resting PCWP. PATIENTS: 20 patients with CHF, New York Heart Association functional class IIb-IV, all with a normal QRS duration (< or = 120 ms). INTERVENTIONS: Temporary pacing wires were positioned to enable VDD-LV pacing and a pulmonary artery catheter was inserted for measurement of PCWP, right atrial pressure, and cardiac output. RESULTS: In patients with a PCWP > 15 mm Hg (n = 10), cardiac output increased from 3.9 (1.5) to 4.5 (1.65) l/min (p < 0.01), despite a fall in PCWP from 24.7 (7.1) to 21.0 (6.2) mm Hg (p < 0.001). In patients with a PCWP < 15 mm Hg there was no change in PCWP or cardiac output. Combined data showed that PCWP decreased from 17.0 (9.1) to 15.3 (7.7) mm Hg during VDD-LV pacing (p < 0.014) and cardiac output increased non-significantly from 4.7 (1.5) to 4.9 (1.5) (p = 0.125). CONCLUSIONS: Patients with CHF with a normal QRS duration and PCWP > 15 mm Hg derive acute haemodynamic benefit from VDD-LV pacing.

Cardiac Output↗
PubMed2002

Determinants of outcome after heterotopic heart transplantation.

BACKGROUND: Donor availability is currently the major factor limiting the use of heart transplantation as a treatment for severe heart failure. Heterotopic heart transplantation may address this issue by allowing the use of smaller donor organs, which otherwise may not be used. METHODS: We analyzed the outcome of 42 consecutive, adult heterotopic transplantations performed between 1993 and 1999 at our center and compared them with the 303 consecutive orthotopic transplants performed in adult patients during the same period. METHODS: Univariate analysis showed a relative risk for death of 1.8 at 1 year after transplantation for the heterotopic group compared with the orthotopic transplantation group (p = 0.04). Multiple regression analysis using a proportional hazards model showed that donor-recipient size-mismatch, i.e., donor body surface area < or =75% of recipient body surface area (p = 0.0001), donor age (p = 0.0001), and use of a female donor (p = 0.04) were significant risk factors but heterotopic transplantation per se was not. A Kaplan-Meier survival analysis of heterotopic vs orthotopic transplantation showed that 30-day survival was 76% vs 87%. By 1 year, this was 59% vs 74%. At 3 years, the comparison was 56% vs 69%. Repeating this analysis after sub-dividing the heterotopic group into those size-matched vs size-mismatched, the 1-year survival was 81% vs 45%, respectively (p = 0.02). CONCLUSIONS: Heterotopic transplantation using a size-matched graft resulted in similar survival to that seen after orthotopic transplantation during the same period. Heterotopic transplantation with an undersized graft resulted in significantly decreased survival.

Cause of Death↗