Calcium-channel blockade as an adjunct to heterogeneous delivery of cardioplegia
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Nifedipine improved cardiac function during simulated heterogeneous cardioplegia in dogs. This calcium-channel blocker demonstrated significant benefits in maintaining cardiac output and regional function following cardioplegic arrest.
Area of Science:
- Cardiovascular Physiology
- Surgical Research
- Pharmacology
Background:
- Clinical cardioplegia often results in heterogeneous myocardial perfusion.
- This heterogeneity can lead to impaired cardiac function post-arrest.
- Investigating adjuncts to cardioplegia is crucial for improving patient outcomes.
Purpose of the Study:
- To evaluate nifedipine and lidoflazine as adjuncts to cold crystalloid cardioplegia.
- To assess their efficacy in a canine model simulating heterogeneous cardioplegia.
- To determine the impact on regional and global cardiac function.
Main Methods:
- A canine model was used to simulate heterogeneous cardioplegia via circumflex coronary artery ligation.
- Animals received nifedipine or lidoflazine before aortic clamping.
- Cardiac function was assessed using sonomicrometry for regional function and hemodynamic parameters (left atrial pressure, cardiac output, stroke work) for global function.
Main Results:
- Control dogs showed significant impairment in systolic shortening, stroke work, and elevated left atrial pressure.
- Lidoflazine offered no significant benefit.
- Nifedipine administration resulted in preserved left anterior descending systolic shortening, near-complete stroke work recovery, and minimal change in left atrial pressure, with all dogs achieving target cardiac output.
Conclusions:
- Nifedipine effectively mitigated the negative effects of heterogeneous cardioplegia in this canine model.
- Calcium-channel blockade, specifically with nifedipine, appears beneficial in managing heterogeneous cardioplegia.
- These findings suggest a potential clinical utility for nifedipine in cardiac surgical procedures involving heterogeneous perfusion.
Abstract:
The clinical situation of heterogeneous cardioplegia was simulated in a canine model by temporary ligation of the circumflex coronary artery during a three-hour interval of cardioplegic arrest. Nifedipine and lidoflazine, administered prior to aortic clamping, were evaluated as adjuncts to cold (2 degrees C) crystalloid cardioplegia. Assessment was made of regional function (sonomicrometer systolic shortening) and of global function by measuring left atrial (LA) pressure at constant cardiac output (CO), aortic pressure, and heart rate, and by measuring stroke work at constant LA pressure, aortic pressure, and heart rate. Among 14 control dogs, only 7 could achieve a CO of 5 liters per minute following cardioplegic arrest. Left anterior descending coronary arterial systolic shortening recovered to only 86% of prearrest values (p less than 0.05), circumflex coronary arterial systolic shortening recovered only 28% (p less than 0.01), stroke work recovered 59% (p less than 0.01), and LA pressure was 6.7 mm Hg higher (p less than 0.01) than prior to cardioplegic arrest. Lidoflazine provided no statistically significant benefit in these animals (N = 4). However, dogs given nifedipine (N = 6) had very little change in left anterior descending coronary arterial systolic shortening (99% recovery), stroke work (93% recovery), and LA pressure (delta = 0.4 mm Hg). None of these changes was statistically significant. There was some deterioration in circumflex coronary arterial systolic shortening (56% recovery; p less than 0.05). All 6 dogs given nifedipine achieved a CO of 5 L/min following cardioplegic arrest. Clinical cardioplegia is typically heterogeneous cardioplegia. Calcium-channel blockade appears to be useful in this situation.