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Three-hour preservation of the hypothermic globally ischemic heart with nifedipine
Insights
A novel intracellular-like crystalloid cardioplegic solution (ICS) with nifedipine significantly improved heart function after prolonged 3-hour global ischemia. This combination offers superior myocardial protection compared to standard solutions.
Area of Science:
- Cardiology
- Cardiac Surgery
- Cardioplegia Solutions
Background:
- Standard extracellular cardioplegic solutions (CPS) offer limited protection during prolonged global ischemia (GI).
- Previous studies indicated intracellular-like crystalloid solutions (ICS) and nifedipine (N) may enhance myocardial protection.
Purpose of the Study:
- To evaluate the efficacy of a low-sodium ICS with nifedipine (N) for protecting canine hearts during extended 3-hour GI under hypothermia.
- To compare ICS +/- N with standard CPS +/- N during prolonged cardiac ischemia.
Main Methods:
- Canine hearts underwent 3 hours of GI at 10°C with cold (4°C) CPS or ICS, with or without N (200-400 µg/L), administered multidose every 30-45 minutes.
- Systemic hypothermia (25°C) was maintained throughout the procedure.
- Post-ischemic cardiac function was assessed by measuring stroke work index (SWI) and left ventricular pressure derivative (LV dP/dt).
Main Results:
- After 3 hours GI and 2 hours reperfusion, SWI decreased by ~50% in CPS, ICS, and CPS + N groups.
- The ICS + N group demonstrated excellent preservation, with LV SWI and LV dP/dt returning to pre-ischemic levels.
- Cardiac output in the ICS + N group increased above baseline and responded appropriately to volume loading.
Conclusions:
- A low-sodium ICS containing nifedipine is highly effective for protecting the heart during extended ischemic intervals.
- The composition of the cardioplegic solution significantly influences the effects of nifedipine on post-ischemic cardiac performance.
Abstract:
We have previously shown that an intracellular-like crystalloid cardioplegic solution (ICS) provides superior protection to normothermic canine hearts subjected to 1 hour of global ischemia (GI) in comparison to a standard extracellular-type clinical cardioplegic solution (CPS). The addition of a calcium antagonist, nifedipine (N), to CPS was shown to be salutory. The new experiments used systemic hypothermia (25 degrees +/- 1 degrees C) and multidose (500 ml) cold (4 degrees C) CPS or ICS with and without N (200 to 400 micrograms/L) every 30 to 45 minutes during GI intervals of 3 hours at a resultant myocardial temperature of 10 degrees +/- 2 degrees C. The results show that after 3 hours of GI and 2 hours of observation stroke work index, (SWI) decreased to 50% +/- 10% of control for the CPS, ICS, and CPS + N groups. The ICS + N group had excellent preservation with left ventricular (LV) SWI and first derivatived left ventricular pressure (LV dP/dt) equal to the preischemic valve. Cardiac output was increased above control levels and responded normally to volume loading. Possible mechanisms of nifedipine and CPS interactions are discussed. It is concluded that a low sodium ICS containing N is highly efficacious for long ischemic intervals and that composition of the CPS strongly influences the effects of N on postischemic performance.