#A 60 year old woman presents to the clinic for a 6-month follow-up examination newly diagnosed HTN,which has not been adequately controlled by dietary and lifestyle changes.
Past Medical History: Angina and asthma.
On examination- Vital signs: BP 160/99 mm Hg, HR 55 beats/min. Allergies: Sulfa-based drugs. Medications: Albuterol inhaler, fluticasone inhaler, and nitroglycerin sublingual tablets.
Management: Diuretics and beta-blockers are first-line agents for treating HTN. Because this patient has asthma, beta-blockers should be avoided. Calcium channel blockers are favorable therapeutic options in patients with both angina and HTN. Because her heart rate is low, diltiazem and verapamil are not optimal choices because they can slow down AV nodal conduction. A long-acting dihydropyridine, amlodipine, was started.
CASE DISCUSSION-
Calcium channel blockers inhibit l-type calcium channels in cardiac and smooth muscle. As a result, inhibition of calcium influx into cells occurs, causing a decrease in myocardial contractility and rate, resulting in reduced oxygen demand. Cardiac rate is slowed by the ability of calcium channel blockers to block electrical conduction through the atrioventricular{AV) node. In addition, calcium channel blockers can reduce systemic arterial pressure by relaxing arterial smooth muscle and decreasing systemic vascular resistance.
Both diphenylalkylamines (verapamil) and benzothiazepines (diltiazem) exhibit effects on both cardiac and vascular tissue. With specificity for the heart tissue, these two types of calcium channel blockers can slow conduction through the AV node and are useful in treating arrhythmias. The dihydropyridines (nifedipine is the prototypical agent) are more potent peripheral and coronary artery vasodilators. They do not affect cardiac conduction, but can dilate coronary arteries. They are particularly useful as antianginal agents. Bepridil is unique in that it blocks both fast sodium channels and calcium channels in the heart. All calcium channel blockers, except nimodipine and bepridil, are effective in treating HTN.
Verapamil and diltiazem can both cause sinus bradycardia and may worsen CHF. Constipation has been associated with verapamil use. The dihydropyridines often cause symptoms associated with vasodilatation, such as facial flushing, peripheral edema, hypotension, and headache. Because dihydropyridines are potent vasodilators, they can cause reflex tachycardia, which may precipitate palpitations, worsening angina, or MI.
