Experimental studies on the electrocardiogram of the dog

P-Wave Terminal Force in Dogs With Myxomatous Mitral Valve Disease

P-wave terminal force (PTF) is accepted as an electrocardiographic criteria to assess left atrial abnormalities in humans. In this study, the applicability of PTF in dogs with myxomatous mitral valve disease (MMVD) was evaluated, and compared its ability to identify left atrial dilatation with 4 other P-wave derived parameters. Seventy-four dogs with echocardiographically diagnosed MMVD were recruited for this prospective cross-sectional study. Also, 47 healthy dogs were included to serve as controls. All dogs underwent physical, electrocardiographic and standard echocardiographic examinations prior to enrollment. Electrocardiographic measurements were obtained from simultaneous recordings at three different locations for precordial lead V₁. PTF was defined as the deflection following the second half of the P-wave, and was best documented at the first and third right intercostal spaces. In those locations, the P-wave was negative and P-wave terminal force was recognized as a positive undulation in baseline following P-wave. P-wave terminal force and P-wave duration measured from recordings obtained at either the first or third right intercostal spaces had poor to weak correlations (P < .05) with echocardiographic surrogates of cardiac remodeling and congestion. In dogs with MMVD, only P-wave duration and P-wave area distinguished normal and dilated left atria (P < .05). In conclusion, PTF had positive polarity and was best recorded when precordial lead V₁ electrode was placed at the most cranial right intercostal locations. PTF failed to reliably identify left atrial enlargement in dogs with MMVD.

Development and assessment of a novel precordial lead system for accurate detection of right atrial and ventricular depolarization in dogs with various thoracic conformations

OBJECTIVE

To assess recording accuracy of right atrial and ventricular depolarization during 12-lead ECG when precordial lead V₁ was positioned at each of 5 locations on the thorax of dogs with various thoracic conformations.

ANIMALS

60 healthy client-owned dogs.

PROCEDURES

20 dogs were allocated to each of 3 groups (brachymorphic, mesomorphic, or dolichomorphic) on the basis of thoracic conformation. Each dog remained unsedated and was positioned in right lateral recumbency for a series of five 12-lead surface ECGs, with V₁ located adjacent to the sternum in the fifth intercostal space (ICS; control), at the costochondral junction (CCJ) of the right first ICS (1st-R), at the CCJ of the right third ICS, at the right third ICS where the thorax was the widest, and at the CCJ of the left first ICS. Electrocardiographic variables were compared among the 5 ECG tracings.

RESULTS

When V₁ was at the control location, the P wave was positive for all dogs; however, consistent recording of right atrial and ventricular depolarization (ie, R wave-to-S wave ratio [R/S] < 1) occurred more frequently for brachymorphic dogs (16/20) than for dolichomorphic (7/20) and mesomorphic (6/20) dogs. When V₁ was at the 1st-R location, the P wave was negative for most dogs, and R/S was < 1 for the majority of dogs in the brachymorphic (19/20), mesomorphic (17/20), and dolichomorphic (16/20) groups. The median R/S for V₁ at the 1st-R location was significantly lower than that for the other 4 V₁ locations.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that placement of V₁ at the 1st-R location provided correct evaluation of right atrial and ventricular depolarization in most dogs regardless of thoracic conformation.