Case Studies In Small Animal

Cardiovascular Medicine

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Case 30

Discharge Instructions

bulletMax had an echocardiogram, ECG, and Holter monitoring performed while he was here in the hospital. His underlying cardiac function is normal, however it is very possible that he had an arrhythmia which caused him to faint this week. The Holter monitor is a 24 hour ECG that records his rhythm for a day to give us a better idea of the extent of his arrhythmias. The results will take 10-14 days to return. In the meantime we recommend he be treated with antiarrhythmic therapy. Please give him sotalol 40 mg (1/2 tablet) twice daily.
bulletThank you for bringing Max to the VMTH. He is a wonderful dog! Please don't hesitate to call Dr. Adin with any questions or concerns.

One Week later

bulletOnce the Holter monitor results were known, Max's owners were telephoned and instructed to increase his dose of sotalol to 80 mg BID.

One Month Later

Presenting Complaints


Pertinent History

bulletMax presented to the referring veterinarian following an acute collapse in which Max lost consciousness and was paddling and having tremors. The referring veterinarian performed an ECG and thoracic radiographs. Max was in sinus tachycardia and radiographs were unremarkable. Max presented to the VMTH following a similar episode one month ago. An ECG, an echocardiogram, and a Holter monitor were performed. A diagnosis of Boxer cardiomyopathy causing malignant ventricular tachycardia was made. Max was initially treated with 40 mg sotalol BID , but has been treated with 80 mg sotalol BID since the Holter monitor results were known. The owner reports that Max has been doing well and has become slightly more active since therapy was begun.

Physical Examination

bulletBAR-H. T=101.6, P=64, R=28. MM pink and moist. Pulse quality fair.
bullet Smooth, full hair coat with 5X5 cm clipped areas on the right and left ventrolateral and dorsolateral thorax with regrowth evident. No masses noted. Eyes, ears and nose are clean and free of discharge. Musculoskeletal system is symmetrical and well developed. Auscultation of the thorax reveals pronounced sinus arrhythmia and clear, eupneic respiratory sounds. A grade II/VI left basilar murmur is ausculted (previous echo showed no abnormalities, including a normal aortic blood flow velocity, thus this is most likely a flow murmur), no crackles or wheezes detected. Abdominal palpation was unremarkable. Prepuce is clean and free of discharge. All palpable lymph nodes are WNLs.


bulletBoxer cardiomyopathy of the type characterized by malignant ventricular arrhythmias without myocardial failure


bulletS/O: See history and physical above. A: Max seems to be responding well to sotalol treatment. No further episodes have occurred since the initial events. P: Monitor Max's ECG via a 24 hour Holter monitor. Continue on 80 mg sotalol PO BID, pending results of Holter.
bulletHolter: The total number of premature ventricular complexes in this 24-hour period was 9451 which is increased over the previous Holter of 5300. However, on this Holter the majority are single beats with only 5 triplets and 21 couplets. Examination of the recorded tracings shows that the coupling interval is greater than on the previous Holter and that the reported R on Ts are not actually present. This is a vast improvement over the previous Holter in which sustained malignant VT was noted. I called the owner with the results and explained that the Holter results were good and show a positive response to sotalol. There is a caveat that this is only 24 hours and may not be a true representation of every day. However, this test is the best that we can do to assess arrhythmias at this time. Max will continue on sotalol 80 mg BID and return for a recheck in 3 months or sooner if Max has a problem.

Two Months Later

Presenting Complaint


Pertinent History

bulletTwo nights ago, Max ran into a table and collapsed. Last night at 2AM he collapsed again. He collapsed again today on the stairs of the teaching hospital. By the time he was taken to ICU he was in sinus rhythm.
bulletHe has been diagnosed with malignant ventricular tachycardia due to Boxer cardiomyopathy.
bulletHis cardiac rhythm was monitored with a Holter monitor on two occasions. The second Holter results showed improved rhythm and response to therapy.
bulletHe receives sotalol 80mg BID.

Physical Examination

bulletGeneral: BARH. Weight 27kg; P 70bpm; R 48/min.
bulletCV: Max's heart rhythm is a slow sinus rhythm. One PVC was seen on ECG. Soft systolic murmur ausculted. Mm pink, good femoral pulses, no jugular pulses present.
bulletThe remainder of the physical exam was wnl.


bulletAcute collapse
bulletMalignant ventricular tachycardia due to Boxer cardiomyopathy

Clinical Diagnoses

bulletBoxer cardiomyopathy with ventricular tachycardia

Plans and Progress Notes

bulletProblem 1 - Acute collapse. S/O: P 70, RR 48. Max has shown no sign of collapse since he was admitted. Continuous ECG monitoring in the ICU revealed only occasional single PVCS. He has an IV catheter so lidocaine can be administered if ventricular tachycardia is observed. He urinated on his walk. He eagerly ate his P/D dinner. A: He appears well between collapsing episodes with predominantly sinus rhythm. P: Continue to observe him for ventricular arrhythmias.
bulletProblem 2 - Malignant ventricular tachycardia. S/O: His ECG has shown sinus rhythm all day. One PVC was seen while he was being examined in Cardiology at 6:30PM; one PVC was seen and recorded at 9:30PM. A: No sign of malignant ventricular tachycardia is present. P: Continue treatment with sotalol, add procainamide therapy. Continue continuous EKG monitoring.


bulletEchocardiogram: IVS(d) 1.1cm, LVEDD 2.9cm, LVESD 2.9cm, FS 26%, LVFW(d) 0.9cm, Ao:LA 1.9:2.9cm. All valves competent and no abnormalities noted.
bulletResting ECG: sinus arrhythmia
bulletContinuous ECG in ICU: Since Max collapsed on presentation, he was monitored in the ICU for 24 hours with a continuous ECG while additional antiarrhythmic therapy was begun. Occasional PVCs were noted.
bulletConclusion: Although not documented at this time, his recent syncopal episodes are due to malignant ventricular tachycardia in light of his previous Holter findings. Max has severe arrhythmias which have been controlled for some time with sotalol. There is no evidence of QT prolongation on the ECG which would suggest a proarrhythmic effect of the drug. It is most likely that his electrical disturbance has progressed and is no longer controlled by sotalol alone. Procainamide (class IA) will be added to the sotalol (class II and III) in an attempt to control the arrhythmias. Max is at high risk for sudden death and would be a potential candidate for an implantable defibrillator. The latter treatment option, however has potential inherent problems and the owner opted for continued medical therapy.

Discharge Instructions

bulletMax stayed in ICU yesterday and overnight for continuous heart monitoring. He has not had any collapse episodes since admission or any severe arrhythmias. Ultrasound of his heart remains normal. We started a second antiarrhythmic yesterday in an attempt to regain control of his arrhythmias.
bulletPlease continue to give Max the sotalol as before: 80 mg (1 tablet) twice daily. Please also give him procainamide 250 mg (1 capsule) three times daily. Watch for potential side effects of this medication such as vomiting or diarrhea and call if these occur.
bulletPlease don't hesitate to call Dr. Adin with any concerns or if Max collapses again. He is a great dog!

Four Years Later

bulletMax has not been examined again at the VMTH. We have not been able to contact the owners. However, his last prescriptions for sotalol and procainamide were filled one year ago when he was nine years of age, which suggests he did well for at least three years following the initial diagnosis.

Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.