The Annals of Thoracic Surgery, Vol 35, 626-632, Copyright © 1983 by The Society of Thoracic Surgeons
Calcium-channel blockade as an adjunct to heterogeneous delivery of cardioplegia
RA Guyton, LM Dorsey, TK Colgan and CR Hatcher Jr
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.
