AV BLOCKS A N D PA C EM A K E R S

‘ZAR’

H A N N A H P E G R A M

SIGNALMENT AND HISTORY

• 26th December: slipped off back legs and ‘not himself’

for the rest of the day.

• End of January: Collapsed in kitchen – hindleg

ataxia/weakness. Was conscious and responsive.

• 6th February: Still lethargic - presents to referring vet

with severe bradycardia. ECG performed and

Theophylline 500mg SID prescribed.

• 9th February: Presented to GUVS Cardiology service.

6yr 4m M GSD

SYNCOPE OR SEIZURE?

Faint = syncope = acute episodic flaccid collapse= cardiovascular

Fit = seizure = acute, central, tonic-clonic etc.= neurological (primary or secondary to metabolic)

Falling over = weakness = generalised = Metabolic, haematological, orthopaedic,

neurological

CLINICAL EXAM

• Bright, alert and responsive

• Good quality pulses

• Mucous membranes pink, CRT < 2 seconds

• 42kg, BCS 4/9

• Bradycardia – 44bpm

• Intermittent brief episodes of tachycardia –

140bpm

DIAGNOSTICS

ECG from referring vet-

Excess P waves, bizarre QRS complexes and variable P-Q

interval

HR of 40bpm

Also an inherent ventricular ectopic rhythm

1° AV BLOCKS

2° AV BLOCKS

Type II

3° DEGREE AV BLOCK

CAUSES OF 3° AV BLOCK

Toxic causes

Localised ischaemia/fibrosis

Tumours within the heart

Myocarditis

Electrolyte disturbances

(Idiopathic)

DIAGNOSTICS

• Haematology and Biochemistry

unremarkable

• Mild increase in Troponin 0.61

(ref range 0-0.15).

• Normal Borrelia antibodies: 3

(ref. Range <4.5)

ECHOCARDIOGRAPHY

ECHOCARDIOGRAPHY

ECHOCARDIOGRAPHY

ECHO FINDINGS

3° AV Block

Escape rhythm of 55bpm

Mild mitral regurgitation

Moderate aortic insufficiency

Normal pulmonary outflow

Ventricular and nodal escape rhythm.

Chambers within normal limits

No masses seen

PACEMAKER IMPLANTATION LifePak

PACEMAKER IMPLANTATION

POST-SURGERY RADIOGRAPHY

POST SURGERY

• Strict Rest and monitoring

• Neck Bandage

• Continuous ECG

• Amoxycillin-clavulanic acid

800mg for 7 days

• Sutures out in 10 days

• No collars,only harness

POSSIBLE COMPLICATIONS

• Seroma formation around pacemaker or jugular sites

• Lead dislodgement

• Pacemaker generator failure

• Pacemaker-related death eg. Endocarditis, neoplasia

• Perioperative mortality

• Lead damage

• Twiddler’s syndrome

PROGNOSIS

The long term outcome is generally fairly good providing the bradyarrhythmia is idiopathic and there is no underlying cardiac or medical disease

• Pacemaker successful in reducing or eliminating clinical signs in over 90% dogs!

• 99% dogs survived pacemaker implantation

• Survival Estimates:

• 1 year : 70-86%

• 3 years: 45-65%

• 5 years: 39%

1 MONTH RECHECK

• No further episodes of collapse or weakness

• 20 minute walk twice a day

• Pacemaker working well

• 57% heart beats produced by pacemaker

• Inherent ectopic rhythm varies and can be as high as 140bpm

•Estimated battery life 7.5- 10 years

THINGS TO REMEMBER

• Only harnesses/haltis, no collars!

• The right jugular vein contains the pacing

lead and should never be used for blood

sampling.

• The pacemaker is explosive

so in the event of death it

should be removed before

cremation.

REFERENCES

Johnson, M., Martin, M. and Henley, W. (2007). Results of pacemaker

implantation in 104 dogs. Journal of Small Animal Practice, 48(1), pp.4-11.

Oyama, M., Sisson, D. and Lehmkuhl, L. (2001). Practices and Outcome of

Artificial Cardiac Pacing in 154 Dogs. Journal of Veterinary Internal Medicine,

15(3), pp.229-239.

Thieman Mankin, K., Dunbar, M., Toplon, D., Ginn, P., Maisenbacher, H. and

Risselada, M. (2014). Rhabdomyosarcoma associated with the lead wire of a

pacemaker generator implant. Veterinary Clinical Pathology, 43(2), pp.276-

280.

Sanchis-Mora, S., Viscasillas, J., Mathis, A., Palacios, C., Brodbelt, D. and

Alibhai, H. (2014). Anaesthetic management and complications of pacemaker

implantation in dogs. Veterinary Record, 175(12), pp.303-303.

Macintire, D. (2012). Manual of small animal emergency and critical care

medicine. John Wiley & Sons.

http://research.vet.upenn.edu/smallanimalcardiology/ECGTutorial/AbnormalECG

s/tabid/4960/Default.aspxAcknowledgements

• Anne French MVB PhD CertSAM DVC

DipECVIM-CA(Cardiology) MRCVS

FHEA

• Jorge Prieto Ramos LdoVet MRCVS

ANY QUESTIONS?