Case Studies In Small Animal

Cardiovascular Medicine

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Case 34

Presenting Complaints

bulletEvaluation For Pacemaker

Pertinent History

bulletChristopher presented to the VMTH Cardiology Service for reevaluation of previously diagnosed 3rd degree AV block. He has a 10 month history of syncopal episodes. His condition has been managed medically with aminophylline 25mg PO TID for the past 6 months.
bulletThe medication initially decreased the syncopal episodes from 10-15 per day to 0-2 per day. Since Christopher's last visit to the VMTH the episodes have again increased to 10-15 per day. The owner reports that the syncopal episodes occur throughout the day and are often precipitated by stress. The owner makes a concerted effort to keep Christopher's environment as calm as possible. They now feel it is in the best interest of Christopher to have a pacemaker implanted. Consequently, he will be transferred to the Soft Tissue Surgery Service for implantation of an epicardial lead and a generator.
bulletThe owner reports that Christopher is an otherwise healthy cat. There is no history of V/D/C/S/PU/PD/PP. Christopher is fed Nature's Recipe Senior Formula. He lives with another healthy cat and 2 dogs.

Physical Examination

bulletGEN: BARH, faints when manipulated; T=100.8, P=120, R=eupneic.
bulletINTEG: clean, full hair coat; no masses, lesions, scaling, or ectoparasites seen.
bulletEENT: cornea, anterior chamber, and lens clear OU; no conjunctival hyperemia or scleral injection; no anisocoria; ears clean AU; nose moist with no discharge.
bulletMS: no gait abnormalities or muscle atrophy; no pain on spinal or joint palpation.
bulletCV: femoral pulses weak and irregular; no jugular pulses appreciated; mm pink, CRT~1sec. Heart difficult to auscult through purring.
bulletRESP: eupneic, purrs when thoracic auscultation attempted.
bulletGI: no discomfort on abdominal palpation; no organomegaly appreciated, smooth gut loops.
bulletGU: neutered male; right and left kidneys palpate smooth.
bulletNS: appropriate mentation. Loss of consciousness not accompanied by urination, defecation or salivation. He is normal both before and after episodes; full neuro exam not performed.
bulletLN: submandibular, prescapular, and popliteal lymph nodes <1cm.

Plans and Progress Notes

bullet11/7/02 - S/O: See history and physical exam. CBC revealed Hb 10.1 gm/dl, Hct 30.1 %, MCV 44.6 fl, MCHC 33.6 gm/dl, reticulocytes 27,000 /ul, slight anisocytosis, slight rouleaux, WBC 5,350/ul, neutrophils 3,098/ul, lymphocytes 1,562/ul, monocytes 70/ul, eosinophils 610/ul, basophils 11/ul, platelets 351,000 /ul, plasma protein 7.5 gm/dl. Serum chemistry revealed anion gap 26 (15-28 MM/L), Na 149 (151-158 MM/L), K 4.7 (3.6-4.9 MM/L), Cl 112 (113-121 MM/L), CO2 total 16 (15-21 MM/L), Ca 9.9 (9.4-11.4 MG/DL), PO4 4.0 (3.2-6.3 MG/DL), creatinine 1.3 (1.1-2.2 MG/DL), BUN 25 (18-33 MG/DL), glucose 146 (73-134 MG/DL), TP 7.4 (6.6-8.4 G/DL), albumin 2.7 (1.9-3.9 G/DL), globulin 4.7 (2.9-5.3 G/DL), ALT 74 (28-106 IU/L), AST 19 (12-46 IU/L), ALP 26 (14-71 IU/L), bilirubin total 0.2 (0-0.2 MG/DL), cholesterol 101 (89-258 MG/DL), GGT 0 (0-4 IU/L). Urinalysis revealed USG 1.037, pH 6.0, protein 1+, glucose negative, ketones negative, bilirubin negative, WBC 0-2, RBC 10-20, caudate cells rare. Initially Christopher was started on 2 ug/kg/min of dopamine; however, this did not produce a substantial decrease in his collapsing episodes. His dopamine CRI was increased to 5mls/hr (5 ug/kg/min). Urination-/defecation-, ingested 10g of Iams Senior Dry and 10ml of water. Second degree AV block with intermittent third degree AV block accompanied by ventricular asystole. Multiple syncopal episodes observed (HR~40bpm), often in conjunction with handling of cat. HR increased to >200bpm after episode, then returned to ~140bpm. SBP 150. A: dopamine CRI appears to be decreasing the frequency of syncopal episodes. Third degree AV block seems to occur only during times of stress. When Christopher is left alone ECG tracing is compatible with Mobitz type II second degree AV block. P: Induction scheduled for 13:00, temporary pacemaker to be placed prior to surgery. Epicardial pacemaker to be placed thereafter. Transfer to surgery prior to procedure.
bullet11/8/02 - S/O: T=101.0, P=220, R=40. Maintained on CRI dopamine @ 5mls/hr prior to induction. Dopamine discontinued for atropine trial, Christopher was non-responsive to atropine continuing to experience syncopal episodes and 3rd degree AV block. Several syncopal episodes were captured on videotape. Premeds administered at 12:30 (oxymorphone + atropine), after 2 periods of 3rd degree AV block lasting ~15sec, heart rhythm normalized. Induced at 14:00, temporary pacemaker placed transvenously prior to surgery.
bulletSurgery: A temporary pacemaker was placed and the heart rate was maintained at 140 beats per minute. A 20 cm midline incision was made beginning at the second sternebrae. The xiphoid process was cut and the diaphragm was incised. Pericardial fat was bluntly dissected. Two stay sutures were placed in the pericardium using 2-0 PDS. A 2cm window was made in the pericardial sac and the epicardium was visualized. A pacemaker lead was implanted in the epicardium. Two simple interrupted sutures were placed in the epicardium to secure the lead using 2-0 PDS. The pacemaker was tested and determined to be pacing the heart appropriately. A 5cm x 5cm pocket was created in the subcutaneous tissues of the right lateral abdominal wall. A tunnel was created through the abdominal wall near the subcutaneous pocket. The pacemaker lead was passed through the diaphragm, through the tunnel, and connected to the pacemaker generator. The generator was secured to the abdominal wall and the subcutaneous pocket was closed around the pacing generator. A 1cm incision was made in the muscle of the left side of the diaphragm through which a 3 fr chest tube was placed. The chest tube was secured in the diaphragm with a purse string suture using 2-0 PDS. The diaphragm was closed using 2-0 proline in a simple continuous pattern. The chest tube was passed through a 1 cm incision in the abdominal wall on the left side. The chest tube was secured with a purse string and chinese finger suture pattern using 3-0 nylon The xiphoid process was closed with 2-0 proline with 2 simple interrupted sutures. The linea alba was closed with a simple continuous pattern using 2-0 PDS. The subcutaneous tissues were closed with a simple continuous pattern using 3-0 PDS. The skin was closed with a simple continuous intradermal pattern using 2-0 PDS followed by staples.
bulletTechnical Notes: A 4Fx110cm temporary pacing lead was placed prior to anesthetic induction. The permanent pacing lead implanted is a Medtronic model#4951M; IS-1connector; unipolar; epicardial "fish-hook" lead. The permanent pulse generator implanted is a Medtronic KappaSR401; IS-1 connector; bipolar/unipolar generator. The pacing parameters at the time of implant were set as follows: Mode=VVI; Rate=100ppm; Refractory period=330ms; Pule amplitude=4.0V; Pulse width=0.50ms; Sensitivity=2.8mV; Pace and Sense Polarity=UNIPOLAR. Estimated time until replacement is approximately 69 months.
bulletChest tube placed intraoperatively, 22ml aspirated in total, tube pulled at 23:00. Urinary catheter placed post-procedure, 215ml urine produced in total (2.04ml/kg/hr). Received LRS qs 20mEq KCL @ 15ml/hr and hydromorphone 0.3mg SQ @ 20:00. NPO. ICU bloodwork revealed Hb 15.0 G/DL, pH 7.313, pCO2 38.2 mmHg, pO2 47.6 mmHg, HCO3- 18.5 mm/L, CO2 total 19.6 mm/L, base deficit/base excess -6.3 mm/L, Na 151 mEq/L, K 3.9 mEq/L, Ca (ionized) 1.30 mm/L, HCO3- 18.5 mm/L. Urinalysis revealed clear yellow urine with a specific gravity of 1.023. No syncopal episodes observed post-procedure, paced/self beats observed throughout the night. A: There were no complications associated with the procedure. Christopher has not experienced any syncopal episodes since pacemaker was implanted. He is becoming increasingly fractious. P: Discharge to owners in morning after ECG confirms that pacemaker is functioning correctly. Staple removal + repeat ECG/echo/chest rads in 10-14 days. Restrict activity (if possible) for 30 days. Pacemaker adjustment in 90 days. Amoxicillin 150mg PO BID x 10 days.
bullet11/9/02 - S/O: T=100.8, P=100, R=50. Lung sounds clear in all quadrants, eupneic, mm pink & CRT~1sec, peripheral pulses strong and synchronous. Fluids discontinued, urinary catheter pulled, and ECG discontinued @ 09:00. Urinalysis revealed USG=1.023, urine production calculated @ 2.04ml/kg/hr. A: Christopher is ready to go home. He is stable and would prefer to be left alone. Chest tube and urinary catheter have been pulled. ECG post pacemaker: HR=70 bpm. Periods of Mobitz II AV block and paced beats are present. QRS duration is prolonged and R amplitude is at the high end of normal as before. There are periods where Christopher has short bursts of supraventricular tachycardia where the pacemaker is sensing inappropriately. P: Discharge to owners. Recheck appointments and antibiotic therapy as above. At staple removal may check taurine levels if tachycardia and chamber dilatation does not resolve. We will also adjust the refractory period of the pulse generator to ensure that the pacemaker is sensing appropriately.


bulletEchocardiogram: IVS(d)=0.4 cm, LVEDD=2.1 cm, LVFW(d)=0.4 cm, LVESD=1.5 cm, LA/Ao=1.2, FS=28%. The LV chamber appeared dilated. This was supported by the increased LVEDD measurement. The increased LVESD indicates significant myocardial failure. During episodes of syncope on the echocardiographic table spontaneous echo contrast was observed within the left ventricle. There is no evidence today of regurgitation or enlargement of other heart chambers.
bulletECG: HR is variable; episodes of Mobitz type II AV block as well as 3rd degree AV block accompanied by ventricular asystole (lasting for up to 15sec), QRS complex=0.06sec (max 0.04sec), R wave=0.9mV (max 0.9mV), Q-T interval=0.20sec (max 0.18sec); MEA=-40 (left axis deviation). QRS prolongation, increased amplitude, and altered mean electrical axis is suggestive that his left bundle branch is abnormal. He most likely had periods of bilateral bundle branch block causing his third agree AV block.
bulletThoracic radiographs: Generalized cardiomegaly with prominent pulmonary vasculature.

Clinical Diagnoses

bulletMobitz type II second and 3rd degree AV block
bulletNon-sustained supraventricular tachycardia
bulletMyocardial failure
bulletEpicardial pacemaker implantation

Discharge Instructions

bulletThank you for bringing Christopher to the VMTH; he is a joy to work with!
bulletChristopher presented to the VMTH Cardiology Service for reevaluation of his frequent fainting episodes. He was previously evaluated by both the Neurology and Cardiology Services. Christopher was determined to have a conduction abnormality in his heart.
bulletHis condition has been medically managed for the past 6 months. However the medication appears to no longer be effective as Christopher is again fainting 10-15 times per day.
bulletOn 11/8/02 a pacemaker was placed under anesthesia. There were no complications associated with the procedure. The generator is visible under the skin on the right side of his chest. His chest can be seen twitching when the pacemaker fires.
bulletAn incision was made on Christopher's abdomen. This was closed with skin staples. The staples will need to be removed in 10-14 days. At that time we would also like to recheck Christopher's ECG, chest x-rays, and echocardiogram. On Monday you can call 530-752-1393 to schedule an appointment.
bulletWe also want to see Christopher 90 days from today to make any needed adjustments to the pacemaker to preserve battery life and fine tune the pacemaker. You can schedule that appointment at your convenience.
bulletPlease monitor Christopher's incision for redness, swelling, and discharge. Please call us at the above number if you notice any of these signs.
bulletChristopher should not experience any more fainting episodes. If any occur or if his behavior concerns you in any way, please do not hesitate to call us.
bulletWe are sending Christopher home with 10 days worth of antibiotics in hopes of preventing infection. Please give Christopher Amoxicillin 150mg by mouth twice a day.
bulletThank you again for bringing Christopher to the VMTH; we all love him!

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