Choice of calcium-channels blockers after RA grafting and side
effect
There is a wide range of CB; however, there are three main chemically
divergent groups: dihydropyridines (eg, nifedipine, amlodipine,
nicardipine, clevidipine and nicorandil), phenylalkylamines (eg,
verapamil), and benzothiazepines (eg, diltiazem)26.
The choice of CB to prevent RA spasm has been empirical.
At least theoretically, all CB derivatives can be used to prevent RA
graft spasm; nevertheless it has been demonstrated that dihydropyridine
are the most potent vasodilator27. However, the vast
majority of the studies published in literature used diltiazem as
antispasmodic agent (table 1).
He and colleagues in a in-vitro study found that nifedipine was
19.5-fold more potent than verapamil and 31.6-fold more potent than
diltiazem in RA precontracted with potassium; also, its efficacy on
prevention of RA spasm was shown by the observation that at the usual
plasma concentration, nifedipine significantly reduced RA contraction,
whereas neither verapamil nor diltiazem had any effect on the RA
contraction at equal concentration26.
Diltiazem may have significant negative chronotropic and inotropic
effects. Its early use can increase the requirement for temporary
cardiac pacing in the post-operative period.
Amlodipine is a more selective CB, thereby with less effect on the
myocardium.
However, Kloner et al.28 reported that in patients
with amlodipine, edema occurred in 24%, headache in 8.8% and in
fatigue and dizziness in >4%.
Notably, the potential hypotensive effect of the CB may preclude the use
of other secondary prevention therapies such as beta-blockers or
angiotensin-converting enzyme inhibitors.
Polypharmacy is also an important concern and has been associated with
increased risk of cardiac events29.