Elsevier

The Veterinary Journal

Volume 198, Issue 3, December 2013, Pages 690-695
The Veterinary Journal

A loud right-apical systolic murmur is associated with the diagnosis of secondary pulmonary arterial hypertension: Retrospective analysis of data from 201 consecutive client-owned dogs (2006–2007)

https://doi.org/10.1016/j.tvjl.2013.09.067Get rights and content

Abstract

Canine pulmonary arterial hypertension (PAH) remains under-recognized and under-treated despite being prevalent. This retrospective study investigated whether selected historical and physical examination findings were associated with the diagnosis of canine PAH, defined as tricuspid regurgitation (TR) with a confirmed systolic pressure gradient ⩾35 mmHg. Two hundred and one client-owned dogs (PAH group, n = 96; control group, n = 105) were studied. Dogs in the control group had TR with a confirmed systolic gradient <35 mmHg. All dogs underwent a complete physical examination and a complete echocardiographic assessment.

A loud systolic right-apical murmur (RAM) was significantly associated with TR  35 mmHg. The proportion of dogs with PAH significantly increased as the RAM grade increased, with odds ratios of 4.4–37.6 for Grades 3/6–5/6 (P = 0.004 to <0.001), respectively. A stronger right-than-left apical-murmur had a positive predictive value (PPV) of 83% and was 96% specific for TR  35 mmHg, and when combined with syncope, it had a PPV of 92% and was 92% specific. A Grade ⩾4/6 RAM had a PPV of 85% and was 93% specific. Syncope with a Grade ⩾4/6 RAM had a PPV of 94% and was 92% specific. Ascites combined with a Grade ⩾4 or ⩾5/6 RAM had a PPV of 100% and was 100% specific for TR  35 mmHg. For each of these three murmur categories (Grades ⩾4/6, ⩾5/6, and a louder-right-than-left murmur), when detected with no concurrent ascites or syncope, the positive likelihood ratio varied from 4.6 to 6.4. A loud systolic RAM in dogs with degenerative valve disease is highly suggestive of concurrent PAH.

Introduction

Pulmonary arterial hypertension (PAH) is a heterogeneous condition that increases pulmonary vascular resistance (Kellihan and Stepien, 2012). Some of the least conservative definitions of PAH have included an elevation of the systolic pulmonary arterial pressure to >25 mmHg at rest (MacDonald and Johnson, 2005, Bach et al., 2006, Martin and Corcoran, 2006). The most studied cause of PAH in veterinary medicine is heartworm disease (Sasaki et al., 1992, Johnson and Hamlin, 2000). Primary idiopathic PAH has only been reported in one dog (Glaus et al., 2004), but secondary PAH is relatively common, affecting 14–74% of dogs with acquired mitral regurgitation (MR; Serres et al., 2006b, Kellihan and Stepien, 2012). Moreover, dogs with MR are perhaps living longer than previously due to more effective pharmacotherapy, and might therefore be considered to be at greater risk of developing secondary PAH. Secondary PAH potentially triggers right-sided congestive heart failure (R-CHF), exercise intolerance, or syncope in 23–38% of cases (Johnson et al., 1999, Pyle et al., 2004, Serres et al., 2006b, Kellihan and Stepien, 2012). Nevertheless, PAH is often clinically silent during most of its course.

Clinical signs associated with PAH often also result from co-morbidities and are therefore non-specific. These can include tachypnea, exercise intolerance, cough, dyspnea, lethargy, syncope or collapse, jugular venous distension or pulsation, a gallop rhythm, a split S2, cardiac murmurs, hepatomegaly, and ascites. Therefore, the index of suspicion for PAH is commonly very low, often delaying the eventual diagnosis. As a corollary, because the prevalence of PAH is frequently underestimated, it is under-diagnosed and consequently under-treated, despite the availability of potent medications (Bach et al., 2006, Serres et al., 2006a, Kellum and Stepien, 2007, Moreno, 2007, Atkinson et al., 2009, Brown et al., 2010).

The noninvasive diagnostic study most commonly used for identification and quantification of PAH is Doppler echocardiography, which often has limited availability and can be cost-prohibitive. The diagnostic limitations of this rather prevalent condition emphasize a need for a tangible, practical preliminary test, so that clinicians can include PAH in their differential diagnosis list and can refer appropriate cases for more definitive study. Ideally, such a test should be based on historical and/or physical examination findings rather than on imaging modalities.

In dogs with bilateral systolic apical murmurs related to chronic degenerative valve disease, the right sided murmur can either result directly from tricuspid regurgitation (TR) with a high-velocity jet, or it can be an indirect, secondary audible manifestation of a murmur of MR, radiating from the left to the right hemi-thorax. However, a palpable right apical systolic thrill does not typically radiate from the left to the right and might therefore reflect TR with a high trans-valvular systolic pressure gradient. Nevertheless, palpable precordial TR thrills due to septal leaflet prolapse with an eccentric (lateral) jet or due to tricuspid valve dysplasia (TVD) accompanied by normal pulmonary arterial pressure might be an exception to this general rule.

As right ventricular (RV) afterload is elevated to varying degrees in dogs with PAH, the systolic pressure gradient between the RV and the right atrium (RA) can be extremely high. In theory, if TR is present, its jet velocity can be exacerbated and its murmur grade increased to as high as 5–6/6, i.e. a palpable thrill is present. We hypothesized that a systolic, right apical murmur (RAM) associated with a palpable thrill could raise the index of suspicion for PAH, and that the detection of a right-sided murmur that is louder than a concurrent left-sided murmur would also suggest PAH. We investigated whether selected history and physical examination findings, such as syncope, ascites, and/or a grade ⩾4/6 TR murmur, were associated with the Doppler diagnosis of PAH and its severity.

Section snippets

Case selection and medical records review

Medical records of 350 client-owned dogs consecutively presented for the first time to the Cardiology Service of a university veterinary teaching hospital between 1st January 2006 and 31st July 2007 were retrospectively reviewed. Medical history, clinical signs and a single examiner’s (DGO) physical examination findings, as well as quantitative echocardiographic parameters, were documented and analyzed. The most common diagnosis was degenerative valvular disease, while other diagnoses included

Signalment

The proportion of male dogs and the proportion of intact dogs was not statistically different between the PAH group and the control group (55/96 [57.3%] vs. 67/105 [63.8%], and 39/96 [40.6%] vs. 51/105 [48.6%], respectively).

The mean age was significantly higher in the PAH group than in the control group (11 ± 3 years vs. 9.7 ± 4 years, respectively; P = 0.005). The proportion of dogs with PAH was higher in dogs in their second decade of life, compared to those <10 years old (55.2% vs. 32.8%; OR, 2.52;

Discussion

The most important finding from this study was the strong association between a loud systolic RAM and PAH in dogs when other causes of RAM were ruled out. Whether isolated or combined with either ascites or syncope, a systolic RAM graded ⩾4/6 was associated with PAH, thus supporting both of our hypotheses. The clinical implication is that while dogs without PAH can have TR murmurs, a loud TR murmur strongly suggests PAH, especially in a dog with syncope or ascites. The absence of a loud RAM,

Conclusions

This study supports the hypothesis that preliminary signalment, history, and physical examination findings, a high level of awareness of the disease and its physical manifestations, and a relatively low level of training and equipment can facilitate the early detection of canine PAH.

Conflict of interest statement

None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.

Acknowledgements

Parts of this work have been previously presented in abstract form at the Annual Meeting of the Israeli Subsection of the International Society for Heart Research, Hadassah Ein-Kerem, Jerusalem, April 2008; at the American College of Veterinary Internal Medicine Forum, San Antonio, June 2008; and at the British Veterinary Cardiovascular Society meeting, Loughborough, November 2008. It also represents a portion of a dissertation thesis submitted by Dr. Lenchner to the Koret School of Veterinary

References (25)

  • F. Harrell et al.

    Evaluating the yield of medical tests

    Journal of the American Medical Association

    (1982)
  • L. Johnson et al.

    Clinical characteristics of 53 dogs with Doppler-derived evidence of pulmonary hypertension: 1992–1996

    Journal of Veterinary Internal Medicine

    (1999)
  • View full text