Color Atlas and Synopsis of Electrophysiology, 1st Ed.

33. LONG-TERM MONITORING OF ANTIARRHYTHMIC DRUG THERAPY

Melissa J., Snider PharmD, BCPS, CLS

CASE PRESENTATION

The patient is a 66-year-old woman with a history of paroxysmal atrial fibrillation and hypertension who presents to clinic for routine antiarrhythmic medication monitoring due to being on long-term therapy with dronedarone. She feels well and is adherent to her medications which include dronedarone, metoprolol, hydrochlorothiazide, and warfarin. Last echocardiogram 4 months ago confirmed ejection fraction of 55% to 60%. A 12-lead ECG is performed and reveals atrial fibrillation, duration unknown. Lab work history confirms therapeutic INRs over the past 4 weeks and normal electrolytes and renal function. The recommendation is made for this patient to undergo direct current cardioversion today. Procedure is successful, and the patient is back in normal sinus rhythm. She is to continue on current medications and continue to be closely monitored.

CASE EXPLANATION

Long-term use of any antiarrhythmic medication warrants outpatient monitoring to some degree. The structure and content of this monitoring can vary, but having a protocol or checklist in place is crucial. In the case of BB, it was especially important in this asymptomatic patient who is on dronedarone to be monitored. This is due to this drug’s black box warning regarding the risk of morbidity and mortality in patients with decompensated heart failure or persistent atrial fibrillation, and specific recommendations to cardiovert or discontinue drug if the arrhythmia (atrial fibrillation) recurs. This is one example of many critical interventions that occur through routine monitoring of chronic antiarrhythmic medication therapy.

EPIDEMIOLOGY/ETIOLOGY

• Chronic antiarrhythmic medication for rhythm control is used in nearly one-third of patients with atrial fibrillation in the United States.1

• Rhythm control strategy is more likely to be utilized in younger patients with fewer medical comorbidities, and is also more common in patients having undergone cardioversion or electrophysiology intervention.2

• Risks or toxicities of antiarrhythmic medications need to be weighed against benefits.

 Images Risk may include torsades de pointes, development of heart failure, unwanted effects on heart rate, and organ damage or dysfunction.

 Images Benefits may include the potential for improved quality of life and improved long-term outcomes.

PATHOPHYSIOLOGY

With use of chronic antiarrhythmic medications, consider the following:

• Unique patient characteristics (presence of myocardial ischemia, heart failure, LVH, congenital long QT, etc).

• Drug interactions, known or theoretical.

• Electrolytes, specifically potassium and magnesium.

• Renal function.

• Adverse reactions including toxicities or intolerances.

• Risk of proarrhythmias (prolonged QT, TdP, bradycardia, heart block, wide complex tachycardia, etc).

MANAGEMENT/FOLLOW-UP AND LONG-TERM COMPLICATIONS

Clinical Considerations for Management

• Each class of drugs should be monitored according to the prescribing information.

• Patient encounter for monitoring should always include:

 Images Patient report of arrhythmia symptoms

 Images Medication adherence screening

 Images Drug interaction assessment and education

 Images Adverse drug reaction screening

 Images Completion of objective testing

 Images Consideration of strategy for rate control and stroke prophylaxis as indicated

 Images Verbal and written patient education

• Defining protocols to guide monitoring allows for improved compliance with adhering to requirements.

 Images Example protocols attached (Tables 33-1 and 33-2).

TABLE 33-1 Example Clinical Protocols for Monitoring Long-Term Antiarrhythmic Therapy3,4,5

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TABLE 33-2 Example Alternate Structure of Clinical Protocols for Monitoring Long-Term Antiarrhythmic Therapy3,4,5

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 Images Availability of objective testing on site is ideal as it offers comprehensive monitoring and increases patient adherence (eg, ECG, device clinic, monitor placement, laboratory services).

• Flowsheet documentation of results is beneficial for detecting trends in monitoring, including labs, pulmonary function tests, ECG parameters, etc.

• QT prolongation

 Images Antiarrhythmic medications, especially class III, carry some risk of QT prolongation at varying degrees.

 Images Consider all factors that can increase the QT interval (Table 33-3).

 Images QTdrugs.org is an excellent reference for QT-prolonging medications.7

TABLE 33-3 Factors That Increase the QT or QT-U Interval6

 

• Bradycardia

• Hypokalemia

• Elderly

• Female

• Hypomagnesemia

• Hypocalcemia

• Use of drugs that block IKr potassium channels or prolong QT interval (class III or Ia antiarrhythmics, antibiotics, antidepressants, antiemetics, antihistamines, and antipsychotics are common classes containing QT prolonging medications)

Operational Considerations for Management

• Consider the design and structure of how antiarrhythmic medication monitoring will be done.

• Pharmacist monitoring of outpatient antiarrhythmic medication therapy has been shown to improve patient adherence to recommended testing protocols and to help identify adverse events and clinically significant drug interactions.8

• Pharmacist monitoring of antiarrhythmic drug therapy in an outpatient clinic provided cost benefits to the patients, cost savings to the institution, and efficiency for the electrophysiology program.8

 Images Allows electrophysiologists more time in other activities.

• Therefore, consideration may be given to the development of a pharmacist-run, physician-supervised antiarrhythmic medications monitoring clinic.

• Development of such a service may involve:

 Images Developing clinical protocols in conjunction with referring electrophysiologists.

 Images Establishing thresholds for pharmacists to notify supervising or referring physician.

 Images Reviewing clinical protocols regularly.

 Images Forming scheduling templates, that is, 15 minutes for return, 30 minutes for new patients.

 Images Designing billing structure, that is, incident-to, hospital facility fees, or fee-for-service.

 Images Utilizing consult agreements, which in some states allow pharmacists to participate independently in direct patient care activities, that is, independently evaluating patients, performing medication reconciliation, interviewing patients, ordering testing per protocol, performing patient education, and communicating with physician at regular intervals.

CONCLUSION

• Risk versus benefit analysis should be considered for each unique patient case to truly individualize care.

• Operational considerations are essential for ensuring consistent and quality care at any institution prescribing antiarrhythmic medication monitoring.

REFERENCES

  1. Steinberg BA, Holmes DN, Ezekowitz MD, et al. Rate versus rhythm control for management of atrial fibrillation in clinical practice: results from the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) registry. Am Heart J. 2013;165(4):622-9.

  2. Chinitz JS, Halperin JL, Reddy VY, et al. Rate or rhythm control for atrial fibrillation: update and controversies. The American Journal of Medicine. 2012;125(11):1049-1056.

  3. Thomson Reuters Healthcare. Micromedex web site. http://www.micromedex.com. Accessed July 19, 2013.

  4. Sanoski CA. Arrhythmia management: an evidence-based update. In Cheng JWM, Jaso T, Moser L, eds.: Pharmacotherapy Self-Assessment Program, 6th ed. Lenexa, KY: American College of Clinical Pharmacy; 2006:179-204.

  5. Snider M, Kalbfleisch S, Carnes CA. Initial experience with antiarrhythmic medication monitoring by clinical pharmacists in an outpatient setting: a retrospective review. Clin Ther. 2009;31(6):1209-1218.

  6. Ayad RF, Assar MD, Simpson L, et al. Causes and management of drug-induced long QT syndrome. Proc (Bayl Univ Med Cent). 2010;23(3):250-255.

  7. Woosley RL. QT Drug Lists by Risk Groups. Tucson, AZ: Arizona Center for Research and Education on Therapeutics, 2009. Available at http://www.azcert.org/medical-pros/drug-lists/drug-lists.cfm. Accessed July 19, 2013.

  8. Snider M, Carnes C, Grover J, et al. Cost-benefit and cost-savings analyses of antiarrhythmic medication monitoring. Am J Health Syst Pharm. 2012;69(18):1569-1573.