Veterinary Medicine - January 2008 - (Page 28)

CE PEER-REVIEWED The indications and technique for continuous ambulatory electrocardiographic recording in dogs Holter monitoring is a practical but underused diagnostic test available to all practitioners. It can be used to diagnose and assess treatment of arrhythmias, detect cardiomyopathy, identify the cause of syncope, and measure the atrial ﬁbrillation ventricular response rate during treatment. Justin D. Thomason, DVM, DACVIM (small animal internal medicine); Tiffany L. Fallaw, BS, RVT; and Clay A. Calvert, DVM, DACVIM (small animal internal medicine) C ontinuous ambulatory electrocardiographic recording is a noninvasive test used to evaluate heart rhythm disturbances and to help diagnose the cause of unexplained syncope or presyncope. The utility of Holter recording lies in the ability to continuously examine the heart rate and rhythm over 24 to 48 hours. In contrast to a one-minute electrocardiogram (ECG), which contains only 0.07% of the 24-hour heart rhythm data, Holter recording permits extended ambulatory activity and diurnal ECG evaluation in a variety of situations and environments over at least one sleep-wake cycle. The physicist Norman J. Holter developed an ambulatory ECG monitor and Justin D. Thomason, DVM, DACVIM (small animal internal medicine) Department of Clinical Sciences Center for Veterinary Health Sciences Oklahoma State University Stillwater, OK 74078 Tiffany L. Fallaw, BS, RVT Clay A. Calvert, DVM, DACVIM (small animal internal medicine) Department of Small Animal Medicine and Surgery College of Veterinary Medicine University of Georgia Athens, GA 30602 reported its usefulness in 1961 after the sudden death of a friend.1 Early recorders were bulky and heavy, but today’s stateof-the-art digital recorders are about the size of a cell phone (e.g. Lifecard CF digital Holter recorder—DelmarReynolds Medical, Delmar, Calif.). Several decades of clinical experience in dogs and people have demonstrated that Holter monitoring is a costeffective tool for diagnosing and assessing heart rhythm disturbances, aiding in sudden death risk-strati cation in cardiomyopathic Doberman pinschers and boxers, and evaluating antiarrhythmic treatment.2-10 Holter recordings are most valuable when made in a patient’s home environment with normal or user-determined periods of activity and timed diary entries describing the patient’s activity and clinical signs. 3. Help determine the differential diagnoses in dogs with syncope and presyncope when heart rhythm disturbances are not evident during auscultation or static ECG recording and when event recording is unavailable. 4. Screen Doberman pinschers and boxers for markers of cardiomyopathy, such as ventricular premature contractions (VPCs). 5. Determine the atrial brillation ventricular response rate of dogs during treatment. 6. Assess the functional integrity of implanted arti cial pacemakers. A number of articles in the veterinary medical literature have described the use of Holter recordings for some of these indications.2,3,7-9,11-16 INDICATIONS FOR HOLTER RECORDING Holter recording is indicated in numerous clinical situations, typically involving the detection and assessment of the severity of supraventricular or ventricular tachyarrhythmias and bradyarrhythmias. It can be used to 1. Evaluate the complexity and frequency of cardiac arrhythmias detected during static ECG recording or auscultation. 2. Assess the ef cacy of antiarrhythmic treatment of heart rhythm disturbances. Evaluating arrhythmia severity When a veterinarian identi es a heart rhythm disturbance on auscultation in an asymptomatic dog and a static ECG records occasional VPCs, it is inappropriate to assume that the arrhythmia is benign. A static ECG records only a brief sample in time, and the arrhythmia is often either more or less severe than estimated on a short electrocardiographic recording.2,10 Not all ventricular arrhythmias are dangerous. In fact, most are hemodynamically insigni cant (Table 1). Slow ventricular tachycardia (< 180 beats/min) 28 January 2008 VETERINARY MEDICINE

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Veterinary Medicine - January 2008 Contents Digital Extra Letters Toxicology Brief Idea Exchange A Challenging Case: Phimosis in a Young Adult Dog The Indications and Technique for Continuous Ambulatory Electrocardiographic Recording in Dogs A Review of Selected Systemic Antifungal Drugs for Use in Dogs and Cats CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - January 2008

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