(Please note: Since PHA 454 will not have been completed by P2 students prior to their year end exam, these questions will go on their P3 year end exam. Regardless, this sample portfolio entry still provide a good examples of how to write a portfolio entry.)
Digoxin is used in atrial fibrillation to control the ventricular rate. It may take up to 6 hours to produce its maximal rate control benefits. Digoxin does not provide good rate control during periods of stress or exercise. However, digoxin has morbidity benefits in patients with heart failure. Due to these characteristics, digoxin is not first line therapy for rate control unless the patient has a history of heart failure.
Calcium channel blockers can be generally divided into two classes: nondihydropyridine (verapamil and diltiazem) and dihydropyridine (e.g. amlodipine). Only the nondihydropyridine calcium channel blockers have a role in ventricular rate control. Both verapamil and diltiazem can be given intravenously and have an onset of 3 – 5 minutes, making them quickly effective. These agents are also available PO making them easy to transition for chronic therapy. Verapmil and diltiazem are able to control heart rate even in the setting of stress and exercise. However, nondihydropyridine agents are contraindicated in patients with heart failure due to their negative inotropic effects which can worsen heart failure. Overall, verapmil and diltiazem are considered first line agents for ventricular rate control in patients with atrial fibrillation who do not have heart failure.
Beta-blockers possess many of the same characteristics as the nondihydropyridine calcium channel blockers, with the additional benefit of being useful in the setting of heart failure. They have a quick onset, are available both IV and PO, and control heart rate during stress and exercise. Beta-blockers are also considered first line therapy for ventricular rate control in patients with atrial fibrillation, even those with heart failure. If a patient with both heart failure and atrial fibrillation needs quick ventricular rate control, a beta-blocker would be the best choice. If a patient with both heart failure and atrial fibrillation needs rate control, but the time frame is not as urgent, digoxin would be a good option.
Amiodarone is an antiarrhythmic drug that possesses beta-blocking effects as well. This makes it a good agent for the dual purposes of possibly converting from atrial fibrillation to normal sinus rhythm and maintenance of sinus rhythm as well as controlling ventricular rate. Amiodarone is not generally used solely for its rate control properties, but rather for its rhythm conversion and maintenance properties. However, a patient receiving amiodarone may not need an additional agent for chronic ventricular rate control as the beta-blocking properties of amiodarone may be sufficient. None of the other agents (digoxin, calcium channel blockers, or beta-blockers) can convert atrial fibrillation to normal sinus rhythm or maintain normal sinus rhythm.
Rhythm control vs. rate control has been a much researched issue in atrial fibrillation patients. All of the studies have demonstrated no mortality benefit of rhythm control over rate control. Rhythm control does generally carry a higher risk of adverse effects, though. Rate control patients must also receive anticoagulation therapy, which also carries a high risk of adverse effects. However, most patients on rhythm control eventually become resistant and must also receive anticoagulation. For these reasons, it is now often the goal of therapy to maintain ventricular rate control rather than rhythm control in most patients.
