What Are PVCs?
In a normal heartbeat the atria (upper or filling chambers of the heart) contract and send a signal to the ventricles (lower or pumping chambers of the heart) to contract. When the ventricle contracts early without the usual signal from the atria it is called a premature ventricular contraction or PVC. If the atria or upper chamber contracts early it is called an APC or atrial premature contraction.
APCs may be a precursor to atrial fibrillation but they are not associated with sudden death. Although single PVCs are not symptomatic, sometimes these early beats come from different sites in the ventricle (multifocal) and or occur in multiples (couplets,triplets). This can lead to ventricular tachycardia or ventricular fibrillation and these rhythms are associated with fainting and even sudden death. In certain breeds such as Boxers or Dobermans PVCs on a screening EKG are a known precursor to DCM (dilated cardiomyopathy) or sudden death.
What Do PVCs Mean in IWs?
PVCs are a sporadic arrhythmia and thus the incidence is not certain in the IW.
In Germany 2.6% of hounds were reported to have PVCs on screening EKGs done at a veterinary hospital in asymptomatic hounds.
In England an incidence of 4% was reported. These screening EKGs were done at shows and at private kennels.
In the Lifetime Cardiac Study (USA) 2.6% of asymptomatic hounds had PVCs on the entry EKG. These EKGs were done at shows or IW gatherings.
Many of these hounds continued in the LCS, and follow-up EKGs were available on 65 hounds with PVCs .
In this population of 65 asymptomatic hounds with PVCs on a screening EKG, 17 or 26.1% did NOT have PVCs on subsequent EKGs. Multiple abnormalities including AVBlock (16.9%) and APCs (12.3%) were noted on follow- up EKGs in this population and were usually transient. 18.4% of this population developed atrial fibrillation during follow up.
Echocardiograms were available on 23 of these hounds. No hound with PVCs as the only arrhythmia had an abnormal echocardiogram. No hound in the PVC only population developed DCM (dilated cardiomyopathy).
Are PVCs Associated with Early Death in the IW?
Date of death and cause of death information was available on 26 dogs and 31 bitches with PVCs. For this population mean age at death was 8.2 years- bitches 8.6 years and dogs 7.7 years.
There were 4 reported sudden deaths- 3 within a year of the tracing with PVCs. In the LCS total database the incidence of sudden death in the general population was 3.9% and in the overall PVC population was 9.6%.
Cause of Death in Hounds with PVCs
Nine hounds had many years of normal EKGs and within a year of developing PVCs 7 had died of osteosarcoma and 2 of lymphoma. Cardiac irritability shown by this arrhythmia may reflect the inflammatory nature of certain malignancies.
|Cause of Death||Dogs||Bitches|
|Euthanized for Rear End Weakness||6||7|
|Post op Bleeding||0||1|
Further Investigation of PVCs in IWs
The IWF supported a study with Dr. K.E. Schmitt to examine the hypothesis that PVCs on a screening EKG in the IW were a benign arrhythmia not associated with structural heart disease or clinical consequences. 19 hounds entered the study with an EKG, holter monitor,blood work (there are metabolic conditions that can cause PVCs), and echocardiogram. On holter exam there were 7 dogs with worrisome ventricular arrhythmias although the screening EKG had shown only benign appearing PVCs. 6 of these hounds were started on medication for the ventricular arrhythmias. At the end of the study period 13 dogs were deceased. 11 were non-cardiac and 2 dogs had sudden death.
The IWF has continued to fund investigation into this arrhythmia. Dr. Bill Tyrrell et al will follow 15 IWs with PVCs on screening EKGS and NO worrisome ventricular arrhythmia on holter monitor. Blood work and echo will be obtained at initiation into the study. The hounds will have yearly echo, EKG and holter monitor and be followed through their lifetime.
This study will hopefully provide data for vets and owners that in THIS population of IWs PVCs ARE a benign arrhythmia .
Hounds are still needed to participate in this study.
In the population of 65 asymptomatic IWs with PVCs on a screening EKG 26.1% did not have them on subsequent EKGs.
In the LCS data the mean age at death in a population of 819 hounds was 7.4 years and mean age at death in the PVC population (65 hounds) was 8.2 years. So certainly PVCs are not a predictor of early death in the Irish Wolfhound.
There were no abnormal Echos reported in this population and no hound in the PVC only population died of DCM. PVCs are NOT a precursor to DCM in the Irish Wolfhound.
The incidence of sudden death in this population was much higher than in the general population (9.6% vs 3.9%). This plus the surprising number of serious arrhythmias found on holter monitors in this population suggest PVCs are NOT ALWAYS a benign arrhythmia in an asymptomatic hound.
All data suggests that IWs with PVCs should have a holter monitor.
PVCs in an asymptomatic hound with a benign holter monitor exam are felt to be a benign arrhythmia in the Irish wolfhound. Data is being collected to examine this hypothesis.
In older hounds with many years of normal EKGs the appearance of PVCs may suggest an underlying malignancy- in the data it was osteosarcoma or lymphoma.
In the population with date of death/cause of death follow-up available, there were 31 bitches and 26 dogs. In most sub populations there were slightly more bitches than dogs but no real difference in sexes could be identified.