Effects of Chronic Heart Failure on the Inotropic Response of the Right Ventricle of the Conscious Dog to a Cardiac Glycoside and to Tachycardia
Why the study?
Do ouabain and tachycardia exert a greater inotropic response in the failing right ventricle compared to the nonfailing right ventricle in conscious dogs?
Population
Conscious dogs before and after chronic right heart failure induced by tricuspid avulsion and pulmonary…
Comparison
Ouabain 20 µg/kg and elevation of cardiac rate… vs The same dogs prior to heart failure induction
Design
Preclinical
Authors
Discussion
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Implication
May indicate heightened inotropic reserve in failing canine RV; leaves open translation to human right heart failure.
Key Points
- To determine how chronic right ventricular heart failure affects the inotropic response to the cardiac glycoside ouabain and to increased heart rate (Bowditch phenomenon) in conscious dogs.
- Evaluated conscious dogs before and after inducing chronic right heart failure via pulmonary stenosis with or without tricuspid avulsion.
- Measured right ventricular segment length, pressure, velocity of shortening (V), dP/dt, and dP/dt/P during ouabain infusion (20 µg/kg) and pacing tachycardia (90 to 240 beats/min).
- Inducing heart failure elevated right ventricular systolic pressure from 25 ± 3 to 59 ± 7 mm Hg and end-diastolic pressure from 3 ± 1 to 16 ± 2 mm Hg, while reducing baseline dP/dt/P from 48 ± 6 to 24 ± 4 sec⁻¹ and V from 26 ± 3 to 15 ± 3 mm/sec.
- In healthy dogs, ouabain increased dP/dt/P by 18 ± 2% and V by 17 ± 2%, while tachycardia increased dP/dt/P by 15 ± 3% and V by 16 ± 3% (19 ± 3% and 21 ± 3% with volume maintenance).
- In dogs with heart failure, inotropic responses were significantly greater: ouabain increased dP/dt/P by 47 ± 5% and V by 48 ± 6%, while tachycardia increased dP/dt/P by 41 ± 4% and V by 51 ± 3%.
Structured PICO
Do ouabain and tachycardia exert a greater inotropic response in the failing right ventricle compared to the nonfailing right ventricle in conscious dogs?
P
Population
Conscious dogs before and after chronic right heart failure induced by tricuspid avulsion and pulmonary stenosis, or by pulmonary stenosis alone
I
Intervention
Ouabain 20 µg/kg and elevation of cardiac rate from 90 to 240 beats/min (tachycardia)
C
Comparator
The same dogs prior to heart failure induction (normal, healthy state)
O
Outcome
Right ventricular (RV) segment length (SL), pressure (P), velocity of shortening (V), dP/dt, and dP/dt/Psurrogate
Cardiac glycosides and tachycardia exert significantly greater positive inotropic responses in the failing heart compared to the nonfailing heart in conscious dogs.
Cite This Study
Vatner et al. (1974) studied this question.