HISTORY / CLINICAL SIGNS: 1 week Hx of weakness & exercise intolerance. Recent episode of collapse. Other chronic problems: hyperadrenocorticism/Cushing’s Disease (well-controlled with Rx: mitotane, SAM-e), mild hip dysplasia, moderate periodontal disease, multiple cutaneous masses, nuclear sclerosis OU.
PHYSICAL EXAM FINDINGS: T 102.0 ยฐF (38.9 ยฐC). P 190 bpm. R panting. BAR. BCS 3.5/9. mm pk/moist. CRT 2 sec. Cardiac arrhythmia. Normal lung sounds. Moderate generalized hepatomegaly.
What is on your differential diagnosis list? What diagnostic tests would you order? Any other questions?
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DIAGNOSTIC TESTS & RESULTS:
- Bloodwork: Stress leukogram. Elevated ALP, mildly increased ALT. Otherwise, unremarkable (no electrolyte abnormalities).
- Thoracic radiographs: unremarkable
- ECG: How would you characterize this heart rate and rhythm? (see image below)
- Cardiology referral: (see results below under โDiagnosisโ)
Based on this patientโs signalment, clinical signs, physical exam findings, and test results, what is your diagnosis, recommended treatment, and prognostic outlook?
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DIAGNOSIS & TREATMENT: Supraventricular Tachycardia (SVT)
Based on this patientโs ECG, she was diagnosed with supraventricular tachycardia, an abnormally fast heart rate in which electric impulses originate from the heartโs AV node or other atrial region (rather than the SA node โ the bodyโs natural pacemaker). Cardiologists initially prescribed this patient diltiazem, a calcium channel blocker to slow AV node conduction, thereby increasing refractory time and slowing heart rate. Upon recheck 1 week later, she was still experiencing tachycardia, so the diltiazem dose was increased. The patient did not tolerate this dose change well, experiencing bradycardia. Upon a subsequent cardio recheck, telemetry was performed, showing an avg. HR of 160bpm with several brief bouts of atrial flutter; SVT persisted. The diltiazem dose was readjusted to the previously lower and well-tolerated dose; amiodarone was added. Amiodarone is primarily a class III anti-arrhythmic, functioning as a potassium channel blocker. Prior to administration, this patientโs thyroid hormone level (normal) was measured since side effects of amiodarone include thyroid changes and liver injury. Thyroid level and liver enzymes will be regularly rechecked to monitor for damage. In this case, the exact underlying cause of SVT was not determined; the atrial flutter is suspected to be due to some underlying primary heart disease. Due to the patientโs age, the owner declined catheter ablation at a specialty referral facility. catheter ablation (in which the aberrant cardiac tissue that is causing the SVT is destroyed using radiofrequency energy) is the only means to cure this type of SVT. Otherwise, medications to control the abnormal rate and rhythm are required (as in this case).
PROGNOSIS: Fair in this case for the long-term, particularly due to the advanced age of the patient and the likelihood that the suspect primary cardiac disease that is triggering the SVT may worsen over time. For the short-term, this patient did well on diltiazem and amiodarone.
Any other questions, comments, or suggestions?
Cardiology strike your fancy? Click HERE to read The Meowing Vet’s comprehensive article on congestive heart failure (CHF) by a boarded veterinary cardiologist.
Unless otherwise stated, these clinical cases are real-life cases that I have managed as a veterinarian in general small animal veterinary practice or else assisted with as a student in vet school. These cases are a great real-world learning tool for vet students and other veterinary professionals. They shall be used for learning purposes and collaboration of knowledge only. These cases are not intended to diagnose or treat any disease by pet owners. – Maranda Elswick, DVM
