Cardiac dysrhythmias frequently follow a myocardial infarction (heart attack)
or result from hypoxia (lack of oxygen to body tissues), hypercapnia (increased
carbon dioxide in the blood), excess catecholamines, or electrolyte imbalance.
Antidysrhythmics are grouped into four classes.
1.Fast (sodium) channel blockers. Fast (sodium) channel blockers are 1A (I)
(quinidine and procainamide), 1B (II) (lidocaine), and IC (III) (encainide,
flecainide).
2.Beta blockers. Beta blockers were discussed previously in this chapter and
discussed in Chapter 15. This includes propanolol (Inderal).
3.Prolong repolarization. Prolonged repolarization is the time when the elec-
trical impulse returns to normal and is ready to fire again. These include
bretylium (Bretylol) and amiodarone (Cordarone).
4.Slow (calcium) channel blockers. Slow (calcium) channel blockers were
discussed previously in this chapter and include verapamil (Calan, Isoptin)
and diltiazem (Cardizem).Antihypertensive drugs
Antihypertensive drugs are used to treat hypertension. Hypertension is classified
as follows.
There are two types of hypertension.
1.Essential hypertension. Essential hypertension affects 90% of patients who
are hypertensive and is caused by conditions other than those related to
renal and endocrine disorders.
2.Secondary hypertension. Secondary hypertension affects 10% of patients
who are hypertensive and is caused by secondary disorders of the renal and
endocrine systems.The exact cause of essential hypertension is unknown. However, there are
nine factors that contribute to hypertension. These are:
- Family history of hypertension.
- Hyperlipidemia.
- African-American descent.
- Diabetes.
- Obesity.
- Aging.
CHAPTER 19 Cardiac Circulatory Medications^355