Clinical usefulness of cardiac event recording in dogs and cats examined because of syncope, episodic collapse, or intermittent weakness: 60 cases (1997-1999)

Holter monitoring in dogs: 24 h vs. 48 h

Holter monitoring has an important role in the diagnosis of cardiac arrhythmias in dogs with underlying heart disease or clinical signs such as intermittent weakness/ collapse or exercise intolerance, and in the assessment of antiarrhythmic treatment efficacy. A typical recording lasts for 24 h, although 48 h or any number of days up to 7 are possible, especially when investigating clinical signs that may not happen during the first 24 h. The objective of this study was to review retrospectively a large number of 48 h Holter recordings obtained from dogs to assess the possible incremental diagnostic yield of the second 24 h period in comparison to the first 24 h. Three hundred and fifty four 48 h Holter recordings were included in the study for analysis. A 48 h Holter recording contributed to a 14.5% increase in the likelihood of documenting the cardiac rhythm during an event of interest; a 24 h recording increased the diagnostic yield from 32.2% to 46.7%. When the recordings were grouped according to the most important rhythm abnormalities (supraventricular arrhythmias group, ventricular arrhythmias group, bradyarrhythmias group, no arrhythmias group), the 48 h Holter monitor contributed to a 5% increase in the likelihood of identifying a relevant cardiac rhythm abnormality, increasing the diagnostic yield from 58% to 63%. This benefit occurred mostly in dogs with iterative or paroxysmal supraventricular arrhythmias. In dogs with bradyarrhythmias or ventricular arrhythmias, an additional 24 h of analysis was useful in only a limited number of cases.

Heart rhythm characterisation during unexplained transient loss of consciousness in dogs

The identification of the heart rhythm during an episode of transient loss of consciousness (TLOC) is considered the reference standard method to elucidate the underlying aetiology. This study aimed to characterise heart rhythm in dogs during TLOC using Holter and external loop recorder monitoring. We retrospectively reviewed 24-h Holter monitoring and external loop recorder tracings from 8084 dogs. Heart rhythms from dogs that experienced TLOC during the recording was analysed to identify rhythm disturbances that occurred during episodes of TLOC. Electrocardiograms (ECGs) were subsequently categorised into Type 1 (ventricular arrest), Type 2 (sinus bradycardia), Type 3 (no/slight rhythm variations), and Type 4 (tachycardia). Transient LOC was documented in 92 dogs over 230 episodes of TLOC. Percentage of cases with ECGs compatible with each classification were as follows: 72.1%, Type 1; 6.1%, Type 2; 20.9%, Type 3; and 0.9%, Type 4. Cardiac rhythm during the TLOC could have been a consequence of a neurocardiogenic mechanism in 46.7% cases, while intrinsic rhythm disturbances of the sinus node or of the atrioventricular node were diagnosed in 31.5% cases. In two cases, tachycardia was the possible cause of the TLOC. ECG patterns in dogs presenting with multiple TLOC episodes were completely reproducible during each episode. TLOC in dogs was primarily caused by ventricular arrest. Most dogs with TLOC had electrocardiographic finding suggestive of a reflex or neurally-mediated syncope, but one third had an ECG more suggestive of a conduction disorder. Distinguishing these two entities could help inform diagnostic, therapeutic, and prognostic plans.

Indications for permanent pacing in dogs and cats

Pacemaker implantation is considered as a standard procedure for treatment of symptomatic bradycardia in both dogs and cats. Advanced second-degree and third-degree atrioventricular blocks, sick sinus syndrome, persistent atrial standstill, and vasovagal syncope are the most common rhythm disturbances that require pacing to either alleviate clinical signs or prolong survival. Most pacemakers are implanted transvenously, using endocardial leads, but rarely epicardial leads may be necessary. To decide whether a patient is a candidate for pacing, as well as which pacing modality should be used, the clinician must have a clear understanding of the etiology, the pathophysiology, and the natural history of the most common bradyarrhythmias, as well as what result can be achieved by pacing patients with different rhythm disturbances. The goal of this review was, therefore, to describe the indications for pacing by evaluating the available evidence in both human and veterinary medicine. We described the etiology of bradyarrhythmias, clinical signs and electrocardiographic abnormalities, and the choice of pacing modality, taking into account how different choices may have different physiological consequences to selected patients. It is expected that this review will assist veterinarians in recognizing arrhythmias that may require permanent pacing and the risk-benefit of each pacing modality and its impact on outcome.

Retrospective Analysis of Indications and Complications Related to Implantation of Permanent Pacemaker: 25 Years of Experience in 31 Dogs

Introduction

Pacemaker implantation is the only effective symptomatic treatment for life-threatening bradyarrhythmias. Major complications observed after implantation of cardiac pacemakers include lead dislocation, loss of pulse generator function, and inadequate stimulation. The aim of this retrospective single-centre study was to analyse the indications for pacemaker implantation and the incidence and types of complications associated with this procedure in dogs treated for symptomatic bradyarrhythmia.

Material and Methods

The retrospective analysis included 31 dogs with symptomatic bradyarrhythmia, implanted with permanent cardiac pacemakers in 1992-2017. The list of analysed variables included patient age, breed, sex, indication for pacemaker implantation, comorbidities, and the incidence of procedure-related complications along with the type thereof.

Results

The most common indication for pacemaker implantation was 3^rd degree AVB, followed by SSS, advanced 2^nd degree AVB, and PAS. Pacemaker implantation was associated with a 35% overall complication rate and 6.45% periprocedural mortality. There were no significant differences in terms of procedure-related complications with regard to age, sex, breed, indications for pacemaker implantation, or comorbidities.

Conclusions

Cardiac pacing is the only effective treatment of symptomatic bradycardia, but as an invasive procedure, may pose a risk of various complications, including death.

Wireless body sensor for electrocardiographic monitoring in dogs and cats

OBJECTIVES

To evaluate the diagnostic utility of electrocardiogram data obtained by a wireless sensor from 36 dogs and four cats with suspected arrhythmias caused by cardiac or systemic diseases.

MATERIALS AND METHODS

Wireless electrocardiographic recordings were obtained via two precordial electrodes attached to an electrocardiogram sensor connected to a smart device via low-power Bluetooth technology. Cardiac rate, rhythm and duration of P-QRS-T waves were evaluated with VisECG® software. Fifteen- to 30-minute wireless recordings were compared to standard electrocardiograms. Furthermore, the wireless sensor was used in 10 dogs and four cats for 24-hour continuous electrocardiogram monitoring at home.

RESULTS

When compared to standard electrocardiogram, equivalent results were obtained for heart rate and duration of different waves. Due to the longer recording time, more arrhythmias were diagnosed with the wireless device in 50% (15 of 30) of animals with arrhythmias. Satisfactory recordings were obtained when the dogs were resting, standing or walking but interpretation of the wireless electrocardiogram signal was not possible during strenuous physical activity.

CLINICAL SIGNIFICANCE

Wireless electrocardiographic monitoring is a reliable and accurate method for identification of heart rate, arrhythmia and duration of electrocardiogram waves. A higher diagnostic yield of arrhythmias was documented with the wireless sensor due to prolonged monitoring. The device offers a good option for the long-term monitoring of canine and feline cardiac rhythm.

Preliminary Assessment of a Novel 14-Day Electrocardiographic Adhesive Patch Monitor in Dogs

Cardiac arrhythmias often are transient and might not be detected using conventional electrocardiographic (ECG) techniques. The adhesive patch monitor (APM) is a single-lead, lightweight, up to 14-day continuous ambulatory ECG monitor. This study aimed to prospectively assess its usability in four boxer dogs considered either to be healthy or to have arrhythmogenic right ventricular cardiomyopathy. Optimal recording was obtained by placing the APM on the left side of the animal's thorax, at the fifth intercostal space, slightly dorsal to the costochondral junction, and oriented either vertically or parallel to the long axis of the heart. In three dogs, the APM remained attached for 14 days. One dog removed the APM after 59 hr. Skin irritation was documented in all dogs and resolved spontaneously after removal of the APM. The analyzable time was >93% of the total wear time and recordings provided an unambiguous rhythm diagnosis at rest. Walking, running, or playing caused intermittent motion artifact that could impair ECG interpretation. APM results were comparable to those obtained with 24-hr Holter monitoring. Extended continuous ECG monitoring with the APM is feasible in boxer dogs and provides interpretable recordings.

Holter monitoring of small breed dogs with advanced myxomatous mitral valve disease with and without a history of syncope

Background

Syncope is a transient loss of consciousness occasionally occurring in dogs with advanced myxomatous mitral valve disease (MMVD).

Objective

(1) To study ECG changes during syncopal episodes in dogs with advanced MMVD and (2) to compare the occurrence of arrhythmias and changes in heart rate variability (HRV) between dogs with advanced MMVD with and without a history of syncope.

Animals

Forty‐three privately owned dogs (<15 kg) with advanced MMVD: 21 with and 22 without a history of syncope.

Methods

Prospective study with dogs recruited for an evaluation including history, physical examination, echocardiography, and arrhythmia and HRV analysis performed on 24‐hour Holter recordings.

Results

A syncopal episode was observed during Holter monitoring in 4 dogs: 3 dogs had sinus rhythm and 1 dog had sinus arrest followed by escape rhythm. An arrhythmia variable representing sinus arrhythmia was significantly lower in dogs with a history of syncope than in those without (P = .008). Eight of 26 HRV variables were significantly different between dogs with and without a history of syncope.

Conclusions and Clinical Importance

Compared with dogs without a history of syncope, dogs with advanced MMVD and a history of syncope did not have a higher occurrence of arrhythmias, but had less sinus arrhythmia, and had changes in HRV variables representing decreased overall HRV, decreased parasympathetic, and increased sympathetic modulation of heart rate.

Novel cutaneous use of implantable loop recorders in two dogs with unexplained episodes of collapse

Determining the cause of episodes of collapse can be difficult. Even in patients with frequent collapsing episodes due to cardiac causes, diagnostic surface electrocardiogram and 24 hr ambulatory electrocardiographic (Holter) monitoring are sometimes inconclusive. Event monitors with multiple leads can be challenging to use in veterinary medicine over long periods of time due to lead dislodgment. Implantable leadless loop recorders (ILRs) are useful, but owners are sometimes unwilling to have an ILR implanted due to the associated risks and/or costs. In this case report, the authors describe the use of cutaneously placed ILRs in two dogs with unexplained episodes of collapse/exercise intolerance. Data recorded provided clinically useful information. Cutaneously placed ILRs can be used effectively in veterinary medicine to evaluate patients with unexplained episodes of collapse.

Implantable loop recorders: a viable diagnostic tool in veterinary medicine

OBJECTIVE

The purpose of this study was to investigate whether implantable loop recorders could be used in the diagnosis of unexplained collapse in dogs.

METHODS

The medical records of six dogs presented to the University of Liverpool Small Animal Teaching Hospital between May 2003 and October 2006 for further evaluation of intermittent syncopal episodes, collapse or episodic weakness, were reviewed. All these dogs underwent standard investigations and had implantable loop recorders placed.

RESULTS

A provisional diagnosis of supraventricular tachycardia was made in one dog, and diagnoses of exclusion of arrhythmogenic right ventricular cardiomyopathy and idiopathic epilepsy was made in two dogs. One dog suffered no further syncopal episodes, a diagnosis was not reached in another dog and the final dog was lost to follow-up.

CLINICAL SIGNIFICANCE

The implantable loop recorder can be used successfully for the diagnosis of unexplained collapse in dogs.

Syncope secondary to transient atrioventricular block in a German shepherd dog with dilated cardiomyopathy and atrial fibrillation

This case report describes transient atrioventricular block as the etiology for syncopal events in a 6-year-old male German shepherd dog with atrial fibrillation and dilated cardiomyopathy. The arrhythmia diagnosis was obtained via Holter monitoring. Medical treatment with a sustained-release preparation of theophylline, as an additive to the standard congestive heart failure treatment (benazepril, furosemide and pimobendan) may have contributed to temporary remission of the syncopal events. However, the congestive heart failure progressed and the dog was euthanized. Veterinarians should be aware of the possibility of transient atrioventricular block causing syncope in dogs with DCM and AF and should be careful in empirically lowering the ventricular response rate if these dogs present with syncopal episodes.

Assessment of an ECG event recorder in healthy dogs in a hospital environment

Ambulatory electrocardiography techniques are superior to standard electrocardiography in evaluating rhythm disturbances in dogs with episodic weakness or collapse. Disadvantages include cumbersome equipment, short recording periods and an inherent delay in trace analysis. A small programmable cardiac event recorder with combined automatic and owner-triggered recording capability was evaluated in 13 healthy dogs in a hospital environment. The unit was well tolerated and produced diagnostic recordings directly to a personal computer, with useful information about continuous heart rate. It detects premature complexes, pauses and bradycardias according to programmed detection thresholds. These events were counted frequently but trace review revealed concerns regarding specificity. Recordings were often triggered by sinus arrhythmia, sinus tachycardia and unclassifiable rate changes rather than by clinically significant arrhythmias. Correct detection of ventricular ectopic complexes, a single supraventricular premature complex, sinus arrest and second-degree atrioventricular block occurred in individual dogs. Visual review of all automatically recorded events was essential and significantly increased the time required for event recording analysis. Manual recordings might be more useful and the overall results suggest that further studies are warranted to evaluate the system in clinical cases in the home environment.

Cardiogenic shock and cardiac arrest

Severe heart disease may cause hypotension and hypoperfusion, and ultimately circulation may cease altogether. These two clinical syndromes are cardiogenic shock and cardiac arrest, respectively. This review summarizes the causes and clinical features of each, and describes the treatment options available to clinicians managing patients in cardiogenic shock.