RETROSPECTIVE STUDIES

Left Atrial Rupture Secondary to Myxomatous Mitral Valve Disease in 11 Dogs Reid K. Nakamura, DVM*y, Emily Tompkins, DVM, Nicholas J. Russell, BVScx**, Sarah A. Zimmerman, DVMyy, Danielle L. Yuhas, DVMxx, Thomas J. Morrison, DVMpppyyy, Michael B. Lesser, DVMxxx

ABSTRACT The purpose of this retrospective study was to evaluate the long-term outcome in dogs with left atrial rupture secondary to myxomatous mitral valve disease. Eleven client-owned dogs met the inclusion criteria for the study. Median age was 11.6 yr (range, 8.3–17.8 yr), and median weight was 5.8 kg (range, 3.8–15.2 kg). Of the 11 dogs, 10 survived the initial 24 hr after diagnosis and 5 of the dogs were still alive at the conclusion of data collection. The median survival of all dogs was 203 days. Dogs with no previous history of congestive heart failure (CHF) at the time of diagnosis had a significantly longer median survival time (345 days) compared with dogs with a previous history of CHF (160 days, P ¼ 0.0038). Outcome of dogs with myxomatous mitral valve disease presenting with left atria rupture was more favorable than previously reported, and dogs without previous CHF survived the longest. (J Am Anim Hosp Assoc 2014; 50:405–408. DOI 10.5326/JAAHA-MS-6084)

Introduction

diagnosis. Consequently, the study concluded that dogs with LAR

Left atrial rupture (LAR) has been described in the veterinary

have a poor short- and long-term prognosis.3 The authors’ ex-

literature as a rare consequence of myxomatous mitral valve disease

perience in the management of LAR secondary to myxomatous

in dogs.

1–3

A study reported that only 5 of 14 dogs diagnosed with

mitral valve disease has been inconsistent with the results of that

LAR secondary to myxomatous mitral valve disease survived to

previously published study.3 As such, the purpose of this current

discharge and 3 of those 5 dogs were euthanized within 35 days of

study was to evaluate the long-term survival of LAR secondary to

From the Advanced Veterinary Care Center ****, Department of Cardiology, Lawndale, CA (R.N., N.R., S.Z., D.Y., T.M., M.L.); and Mid-Atlantic Equine Medical Center, Ambulatory Department, Ringoes, NJ (E.T.).

CHF, congestive heart failure; LAR, left atrial rupture

Correspondence: [email protected] (R.N.)

†

*R. Nakamura’s updated credentials are DVM, DACVECC, DACVIM (Cardiology). R. Nakamura’s present affiliation is Southern California Veterinary Specialty

Hospital, Irvine, CA. x

N. Russell’s updated credentials are BVSc, MVS, FANZCVS, DACVIM

(Cardiology). **N. Russell’s present affiliation is Veterinary Cardiology and Specialty, Santa Monica, CA. ††

S. Zimmerman’s updated credentials are DVM, DACVIM (Cardiology).

xx

D. Yuhas’ updated credentials are DVM, DACVIM (Cardiology).

ppp

T. Morrison’s updated credentials are DVM, DACVIM (Cardiology).

†††

T. Morrison’s present affiliation is Coast to Coast Cardiology, Hermosa

Beach, CA. xxx

M. Lesser’s updated credentials are DVM, DACVIM (Cardiology).

****Advanced Veterinary Care Center has been renamed to VCA Advanced Veterinary Care Center.

ª 2014 by American Animal Hospital Association

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myxomatous mitral valve disease in dogs diagnosed via echocar-

study. There were 6 castrated male dogs and 5 spayed female dogs.

diographic evaluation.

Breeds included were the Chihuahua (n ¼ 2), toy poodle (n ¼ 1),

Materials and Methods

shih tzu (n ¼ 1), miniature schnauzer (n ¼ 1), Jack Russell terrier

The medical records database at VCA Advanced Veterinary Care

(n ¼ 1), Cavalier King Charles spaniel (n ¼ 1), and mixed-breed (n ¼

Center in Lawndale, California was searched for all dogs with

1). Median age was 11.6 yr (range, 8.3–17.8 yr) and median body

a diagnosis of a LAR secondary to myxomatous mitral valve disease

weight was 5.8 kg (range, 3.8–15.2 kg). Reported clinical signs in-

between January 1, 2009 and May 1, 2012. Dogs were included in

cluded weakness or collapse (n ¼ 7), rapid respiratory rate (n ¼ 6),

whippet (n ¼ 1), papillon (n ¼ 1), Welsh springer spaniel (n ¼ 1),

the study if they had a complete echocardiographic examination

coughing (n ¼ 4), vomiting (n ¼ 1), and loud borborygmi (n ¼ 1).

diagnosing the LAR. The echocardiogram had to be performed by

Five of the 11 dogs had been treated for decompensated left-sided

a board-certified cardiologist or a cardiology resident under the

congested heart failure prior to the diagnosis of a LAR for a median

supervision of a board-certified cardiologist to be included in the

duration of 160 days (range, 47–710 days). Treatment of those 5

study. The echocardiographic diagnosis of a LAR was based on

dogs included furosemidea (n ¼ 5), angiotensin converting-enzyme

the presence of the following four criteria: (1) myxomatous mitral

inhibitorsb (n ¼ 5), pimobendanc (n ¼ 2), and potassium sup-

valve disease and severe mitral regurgitation defined as .50% of

plementationd (n ¼ 1).

the atrium filled by aliased flow of regurgitation on color Doppler

A systolic heart murmur was identified over the left apex in

interrogation; (2) left atrial/ aortic root ratio .1.5:1 on two-

all 11 dogs. They were graded as III/VI (n ¼ 3), IV/VI (n ¼ 5), and

dimensional measurement on the right parasternal short-axis

V/VI (n ¼ 3). Muffled heart sounds were noted in 2 of the dogs.

view; (3) pericardial effusion; and (4) organized echogenic ma-

One of the 11 dogs had evidence of tachycardia (heart rate was

terial in the area of the left atrium within the pericardial space

.160 beats/min). Six dogs were described as tachypneic (respi-

Dogs

ratory rate was .60 breaths/min). Femoral arterial pulse quality

were excluded from the study if the medical record was either

was described as weak in 5 dogs and pulsus paradoxus was

incomplete/missing or the echocardiographic evaluation did not

identified in an additional dog. Jugular venous distension was

fulfill the criteria for a LAR.

noted in 4 dogs.

3–5

suggestive of a thrombus on any echocardiographic view.

Medical records of the dogs were reviewed. Data collected from

Thoracic radiographs were performed in seven dogs. A globoid

the medical records included signalment, history, physical exami-

cardiac silhouette was identified in five of the dogs, and severe left

nation findings, results of radiographic and echocardiographic

atrial and left ventricular enlargement was identified in two other

findings, treatment, and long-term outcome. Median survival time

dogs. Perihilar infiltrates assessed as consistent with decompensated

was reported for the 11 dogs from the day of diagnosis of LAR. The

left-sided CHF was identified in four of the seven dogs.

dogs were then divided into the following two groups: dogs with

The median left atrial/aortic ratio was 2.14 (range, 1.69–2.59).

a previous history of congestive heart failure (CHF) at the time of

Mitral valve prolapse was identified in 5 dogs.6,7 Myxomatous tri-

diagnosis of the LAR and those without a previous history of CHF.

cuspid valve disease was identified in 10 dogs, which was subjec-

The survival data for the two populations were compared.

tively assessed as mild in 9 dogs and moderate in the other dog. Median estimation of peak systolic pulmonary artery pressure

Statistical Analysis

based on the maximum tricuspid regurgitant velocity via the

Descriptive statistics with results were listed as median and range as

modified Bernoulli equation was 29 mm Hg (range, 16–48.8 mm

appropriate. A log-rank test was used to evaluate if there was

Hg). Cardiac tamponade defined as collapse of the right atrium

a statistically significant difference between the median survival

during diastole was visualized in 8 dogs. One dog demonstrated

time of the dogs with a previous history of CHF versus dogs with

evidence of a ruptured chordae tendineae and another dog was

no previous history of CHF. For this study, P , .05 were con-

subjectively assessed as having trivial aortic insufficiency.8,9

sidered significant.

Of the 11 dogs, 4 dogs were discharged from the hospital and 7 dogs were hospitalized for treatment of the LAR. Two of the

Results

4 dogs that were not hospitalized had a systolic blood pressure

A total of 13 dogs were identified. One was excluded because the

measured via Doppler measurement and both were normotensive

medical record could not be located, and another was excluded

(systolic blood pressure .90 mm Hg). Pericardiocentesis was

because a complete echocardiographic evaluation was not per-

performed in 2 of the 4 dogs, in both instances hemorrhagic

formed. Consequently, 11 dogs met the criteria for inclusion in the

effusion was evacuated from the pericardial space. In 1 dog the

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50:6 Nov/Dec 2014

Left Atrial Rupture Secondary to Myxomatous Mitral Disease

volume removed was 28.96 ml/kg and in the other dog the volume

myxomatous mitral valve disease and all 10 dogs survived for at

of pericardial effusion collected was not recorded. One of the

least 30 days after the initial diagnosis, which is an improved

4 dogs had a previous history of treatment of left-sided CHF.

survival duration from the previous study of LAR in dogs.3 The

Of the seven hospitalized dogs, one died in the hospital shortly

difference in survival to discharge recorded in the current study

after echocardiographic evaluation while two others had an episode

compared with previously could be explained by differences in

of cardiopulmonary arrest; both of these latter two dogs were suc-

patient selection criteria. In our report dogs needed to be clini-

cessfully resuscitated and survived to discharge. Of the six remaining

cally stable enough to permit a complete echocardiographic

dogs, two were hypotensive (defined as a systolic blood pressure

evaluation.

,90 mm Hg via Doppler measurement) on admission to the hos-

However, the long term survival of dogs in this study was also

pital. In both hypotensive dogs, cardiac tamponade was evident on

improved compared with the previous study.3 While it is impos-

echocardiogram. One dog was hypotensive for approximately 5 hr

sible to compare the two populations, one difference identified is

while the other dog was hypotensive for approximately 8 hr. In the

that none of the dogs in the previous study received pimobendan,

latter case, the dog was treated with IV crystalloids at 1 ml/kg/hr. In

whereas all hospitalized dogs in this study and 9 of 10 dogs re-

both cases after the elapsed time, systolic blood pressures increased

ceived pimobendan therapy chronically. Studies have shown im-

to greater than 100 mm Hg. Of the six dogs that survived the initial

proved survival times in dogs with myxomatous mitral valve

24 hr of hospitalization, treatment consisted of furosemidee (n ¼ 6),

disease and dilated cardiomyopathy receiving pimobendan.10–12 As

pimobendan (n ¼ 6), oxygen supplementation (n ¼ 4), hydralazinef

pimobendan is an inodilator, it improves contractility and pro-

(n ¼ 2) and intravenous crystalloid therapy g (n ¼ 1). None of the

motes arteriolar vasodilation which has been suggested to in-

dogs that were hospitalized had a pericardiocentesis performed. The

creased left ventricular forward stroke volume and reduce left

median duration of hospitalization for the six dogs was 2 days (range

ventricular and atrial size.13–15 Pimobendan has also been shown

1–4 days).

to reduce left atrial pressure in dogs with experimentally induced

Long-term treatment of the 10 dogs that survived 24 hr after

mitral valve regurgitation as well.16 The role of pimobendan in the

diagnosis included furosemide (n ¼ 10), pimobendan (n ¼ 9),

emergent management of LAR secondary to myxomatous mitral

angiotensin converting enzyme inhibitors (n ¼ 8), potassium

valve disease requires further evaluation.

supplementation (n ¼ 4), aldactazide (n ¼ 2), amlodipine (n ¼ h

i

2) and hydralazine (n ¼ 2).

Previous studies on LAR in dogs reported a male predisposition as well as a possible breed predisposition for dachshunds and

All dogs that survived the initial 24 hr after diagnosis survived

cocker spaniels.1–3 However, our study identified a relatively equal

for at least 30 days after initial diagnosis. Of the 10 dogs, 5 of the

distribution between male and female dogs and none of the dogs

dogs were still alive at the conclusion of the study. The median

in our study were dachshunds or cocker spaniels. This difference

survival of all dogs in the study was 203 days (range 0–760 days).

in signalment and breeds identified may be related to the small

The 5 dogs with a previous history of CHF had all died by the

sample size of our study as well as case selection criteria.

end of the study and had a median survival time of 160 days

Despite the presence of significant cardiac disease as well as

(range 0–252 days). The cause of death in these 5 dogs was eu-

a LAR, none of the dogs in the study were treated with anticoagulant

thanasia due to renal failure (n ¼ 2), euthanasia due to recurrent

therapy. A previous study reported dogs with CHF secondary to

heart failure (n ¼ 1), death in the hospital (n ¼ 1) and 1 dog died

myxomatous mitral valve disease or dilated cardiomyopathy are

at home from an unknown cause but suspected to be secondary to

hypercoagulable compared with normal dogs.17 However, there was

recurrent heart failure. Of the 6 dogs with no previous history of

no clinical suspicion of thromboembolic disease in any of the 10

CHF prior to diagnosis of LAR, 1 dog developed recurrent CHF

dogs with long term follow-up. As such there is no clinical evidence

and was euthanized. The remaining 5 dogs were alive at the

that antithrombotic therapy is indicated in the long-term man-

conclusion of the study. The median survival time of the 6 dogs

agement of dogs with LAR.

with no previous CHF was 345 days (range 40–760 days) which

Limitations to the study are inherent in its retrospective design

was significantly longer (P ¼ 0.0038) compared with dogs with

as well as the relatively small sample size. As previously mentioned,

a previous history of CHF.

the criteria of a full echocardiogram being required for inclusion biased the study population toward a more stable population of

Discussion

dogs with LAR that likely contributed to the improved survival to

The primary finding of this study was that 10 of 11 dogs survived

discharge rates. Management for LAR tended to be similar between

more than 24 hr after initial diagnosis of a LAR secondary to

cases typically involving the use of loop diuretics and pimobendan

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407

in the emergent setting and, therefore, it is impossible to evaluate if one treatment significantly improved survival time over other therapeutic protocols. As our hospital computer system does not track frequency of presentation of different canine breeds, the authors were unable to evaluate if one breed is at higher risk for LAR than others.

Conclusion In conclusion, the long term survival of dogs with LAR provided they survive the immediate period was more favorable in this study than previously reported. Dogs diagnosed with LAR with no previous history of CHF have a significantly longer survival time than dogs with a previous history of CHF. The authors would like to thank Dr. Domenico Bianco DVM, PhD, DACVIM, for his assistance in the statistical analysis of the data in this study. FOOTNOTES a Furosemide tablets; Ranbaxy Pharmaceuticals Inc., Jacksonville, FL b Enalapril maleate tablets; Wockhardt Limited, Mumbai, India c Vetmedin Chewable tablets; Boehringer Ingelheim Vetmedica, Inc., St. Joseph, MO d RenaKare potassium gluconate tablets; Neogen Corporation, Lexington, KY e Salix (furosemide) injection 5%; Intervet Inc., Millsboro, DE f Hydralazine hydrochloride tablets; Par Pharmaceutical Companies, Inc., Spring Valley, NY g Lactated Ringer’s injection; Hospira Inc., Lake Forest, IL h Spironolactone and hydrochlorothiazide tablets; Mutual Pharmaceutical Co., Inc., Philadelphia, PA i Amlodipine besylate tablets; InvaGen Pharmaceuticals, Inc., Hauppauge, NY REFERENCES 1. Sadanaga KK, MacDonald MJ, Buchanan JW. Echocardiography and surgery in a dog with left atrial rupture and hemopericardium. J Vet Intern Med 1990;4(4):216–21. 2. Buchanan JW. Spontaneous left atrial rupture in dogs. Adv Exp Med Biol 1972;22:315–34. 3. Reineke EL, Burkett DE, Drobatz KJ. Left atrial rupture in dogs: 14 cases (1990-2005). J Vet Emerg Crit Care 2008;18:158–64.

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