Case Studies In Small Animal

Cardiovascular Medicine

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Fifth Visit

Case 34

Presenting Complaints

bulletSuture removal

Pertinent History

bulletChristopher presents to the VMTH Cardiology Service for a two week recheck following pacemaker placement.
bulletHe was previously diagnosed with third degree AV block and has had a one year history of syncopal episodes that appear to be precipitated by stress. His condition was initially managed medically with aminophylline 25 mg PO TID. The syncopal episodes decreased from 10-15 per day to 0-2 per day. However, they increased again to 10-15 per day. As a result, a pacemaker was placed.
bulletThe owners report that Christopher has been doing well. He has not had any syncopal episodes and his resting heart rate has been ~108 bpm. He has been eating and drinking well, with no V/D/C/S/PU/PD. His incision site has been healing well, and his course of amoxicillin 150 mg PO BID was finished yesterday.

Physical Examination

bulletGen: BARH. T=not taken, P=80, R=28. MM pink and moist, CRT 1 sec.
bulletInt: Fur growing back at shaved surgical/catheter sites. Ventral midline incision healed.
bulletEENT: OU-cornea, anterior chamber, and lens clear. AU-clean. Nose-moist, no discharge. Throat-no masses. Mild dental calculus.
bulletMS: BCS 5/9. Symmetrical musculature. Did not observe gait.
bulletCV: HR=100, irregular rhythm.
bulletResp: Quiet lung sounds in all fields.
bulletGI: No masses or organomegaly palpated. Smooth bowel loops.
bulletGU: Kidneys palpate smooth.
bulletNS: Appropriate mentation. Complete neuro. exam not performed.
bulletLN: Submandibular, prescapular, popliteal nodes < 1 cm.


bulletPacemaker placement 11/08/02

Clinical Diagnoses

bulletSecond degree and third degree AV block
bulletEpicardial pacemaker
bulletSupraventricular tachycardia
bulletMyocardial failure


bulletThoracic radiographs: Good placement of the epicardial pacemaker. Static cardiomegaly.
bulletTaurine concentrations: Plasma = 90 nmol/ml; whole blood = 489 nmol/ml (both within normal range)
bulletECG: Heart rate variable with alternating periods of supraventricular tachycardia (SVT) @ 200-250 bpm and sinus rhythm @ 110-120 bpm. Pacemaker is pacing inappropriately (firing during periods of SVT). We adjusted the pacemaker to pace appropriately by decreasing the refractory period. Pacemaker was sensing 47% and pacing 53% of the time. Pre-refractory period was 330ms, and post-refractory period was decreased to 150ms.
bulletECHO: IVSd=0.5 cm, LVEDD=1.8 cm, LVESD=1.3 cm, FS=29%, LVFWd=0.5 cm, LA:Ao=1.4:1.1=1.3. Septal bulge. Left ventricular chamber appears dilated. The LVEDD and LVESD are still increased from normal, but are decreased since the previous visit (LVEDD 2.1 cm and LVESD 1.5 cm). Contraction (shortening fraction) appears adequate, but there is still evidence of myocardial failure (increased LVESD).
bulletConclusions: Christopher's clinical signs have improved since placement of the pacemaker. Radiographically, the cardiomegaly appears static. The pacemaker has been adjusted to depolarize appropriately during prolonged pauses in conduction (rate=100 bpm). The heart rate is variable with occurrences of SVT and normal sinus rhythm. The left ventricle is still enlarged with evidence of myocardial failure. Christopher was sent home on 7.5 mg of diltiazem PO TID to control periods of SVT. He will return in ~90 days post pacemaker placement for a recheck.

Discharge Summary

bulletChristopher presented to the VMTH Cardiology Service for a two week recheck following epicardial pacemaker placement.
bulletHe has had no syncopal episodes and has had a resting heart rate of 108 bpm at home. His appetite and attitude have been normal.
bulletOn physical exam, Christopher was bright and alert. He heart rate was 100 bpm, and he had an irregular rhythm. His incision site has healed, so the skin staples were removed.
bulletThoracic radiographs revealed cardiomegaly (heart enlargement) unchanged from previous radiographs. The pacemaker was in a good position. ECG revealed runs of supraventricular tachycardia along with a normal sinus rhythm. The pacemaker was adjusted to fire appropriately when there were prolonged delays in conduction and not during the supraventricular tachycardia episodes. Echocardiogram revealed an enlarged left ventricle with evidence of myocardial failure.
bulletBloodwork was performed to assess taurine concentration. Christopher was started on diltiazem @ 7.5 mg PO TID to control his bursts of supraventricular tachycardia. Christopher should return in three months for further pacemaker assessment.

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