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Saving Benjamin - A Cardiac Case Study
By Merrilee T. Small, DVM, DACVIM (Cardiology)

Case Study: Benjamin (watch video here)
10yo MI Shetland Sheepdog

Family DVM:  Dr. Leatherbury, Atlantic Animal Hospital

History:  Benjamin was initially evaluated at AAH on 11/14/18 for a two-day history of cough. A soft heart murmur was ausculted. Thoracic radiographs were performed and appeared subjectively unremarkable. He was treated for presumptive tracheobronchitis with Clavamox and Cough Tabs. The cough worsened and was reevaluated on 11/21/18. Repeat thoracic radiographs revealed marked progression in cardiac size (Vertebral heart score 14.0) and infiltrate consistent with cardiogenic edema. He was referred to The COVE. Upon discharge from AAH, he vomited and experienced an episode of partial collapse. 

Physical exam on presentation to The COVE 
QAR, WHT - 10kg/22#, ambulatory, normothermic, heart rate 96bpm (inappropriately bradycardic), Grade II/VI systolic murmur over mitral valve, respiratory rate 40bpm with increased effort but clear breath sounds, one palpable testicle.

Diagnostics  
  • A-FAST/T-FAST:  Moderate volume echoic pericardial effusion (PCE). Interstitial lung rockets (ILR, or "B-lines") in all thoracic quadrants. No appreciable abdominal fluid.
  • Electrocardiogram:  No visible p-waves 70bpm. Rule out atrial fibrillation with second degree AV block, vs sinus node dysfunction with junctional escape rhythm.
  • Blood pressure: Mean 82mmHg at admission.
  • Echocardiogram: Mild to moderate echoic pericardial effusion with large, diffuse, organizing thrombus. Mitral and tricuspid valve endocardiosis - severe mitral insufficiency with severe left heart enlargement. A 1.7x1.2cm echoic structure was noted in the left atrial posterior wall - consistent with a mural thrombus. Mild tricuspid insufficiency with moderate right heart enlargement but right atrial collapse in diastole consistent with compromised cardiac filling (tamponade) due to effusion. Markedly dilated caudal vena cava and hepatic vessels without overt abdominal effusion. Dilated pulmonary veins. Mild left ventricular systolic dysfunction. Findings consistent with left atrial rupture.
  • CBC: Stress leukogram, PCV/TS 42%/5.2g/dL
  • Chemistry: SDMA 18ug/dL, BUN 34mg/dL, Creatinine 1.3mg/dL, ALT 158U/L, ALP 17U/L
Assessment
Mitral and tricuspid endocardiosis. Presumptive left atrial rupture with secondary cardiac tamponade. Left congestive heart failure (CHF). Episode of collapse/weakness, likely due to acute cardiac tamponade. Azotemia - rule out prerenal due to acute hypoperfusion vs renal. Elevated hepatic analytes - rule out primary hepatobiliary disease, secondary to acute hypoperfusion.
 
Initial Therapy
  • O2 cage FIO2 40%
  • Furosemide 25mg IV, then 12.5mh PO BID, give additional if needed for increased RR (given once)
  • Pimobendan 5mg PO BID
  • Terbutaline 0.2mg IM BID for bradycardia, switch to theophylline 10mg PO BID when eating
  • Butorphanol 1mg IV/IM/SQ prn TID
  • Hydrocodone/homatropine 5mg: 1.25-2.5mg PO TID as needed
  • Maropitant 10mg IV q 24hr
  • Clopidogrel 37.5mg PO q 24 hours was added once there was no evidence of active hemorrhage
  • Continuous ECG monitoring
  • RR hourly
  • BP q 3 hours until stabilized, then daily
Clinical Course
Benjamin was hospitalized for two days. Congestive heart failure resolved and pericardial effusion decreased in volume, although a thrombus adjacent to heart remained. ECG converted to sinus rhythm with intermittent VPCs and non-sustained runs of accelerated idioventricular rhythm which were not treated. A progressive azotemia developed (BUN 70mg/dL, Creatinine 1.8mg/dL, SDMA 20ug/dL on 11/22 and BUN 54mg/dL, Creatinine 1.2mg/dL, SDMA 19ug/dL on 11/23) and Benjamin became mildly anemic (PCV/TS 34%/5.8g/dL on 11/22 and 38%/7g/dL on 11/23).
 
Follow-up
Benjamin is still with us and doing well! He has had three cardiac rechecks, the last on 4/1/19. The thrombi within his left atrium and pericardial space have resolved, and no pericardial effusion is noted. His energy level is fantastic, and his resting respiratory rates maintain in the 20bpm range. Lab work performed on 4/1/19 revealed BUN 39mg/dL, Creatinine 1.2mg/dL, SDMA 9ug/dL, and Hct 49.2%.
 
 Right lateral 11/21/2018                                                             
Ventral Dorsal 11/21/18

Discussion
Diagnosis of PCE is often fraught with difficulty. Clinical presentation can be very diverse. The first challenge is to confirm its presence, then to identify a cause. Ultrasound is typically required. The most commonly encountered etiologies of PCE are neoplasia and idiopathic pericarditis, but these conditions tend to occur in large breed dogs. The differentials include infectious, systemic inflammatory syndromes, anticoagulant rodenticide toxicity, trauma, cardiac chamber rupture, and, rarely, hypoproteinemia. The presence of PCE in a small breed dog, especially with a history of a heart murmur, should prompt consideration of a left atrial tear/rupture. Common clinical presentation includes a rather acute onset of collapse/syncope, weakness, increased respiratory rate/effort or cough. The most significant diagnostic finding is the presence of an echoic pericardial effusion with a mass lesion on or near the heart consistent with thrombus formation on ultrasound. Other primary differential diagnoses in small breed dogs with mitral valve disease and PCE should include atypical CHF (especially if R or LCHF has already occurred), along with all the other possible causes listed above.

Left atrial "splits" secondary to severe mitral insufficiency were first described by Dr. James Buchanan in the 1960s and  ΚΌ70s, based mostly on necropsy findings (Buchan et al.,  J Am Vet. Radiol 1964). The lesions were the result of high-velocity mitral regurgitant jets impacting the left atrial walls, which were already stretched as the left atrium dilated due to chronic and severe volume load. The "splits" could be partial, penetrating just the endocardium or a portion of the myocardium, or could be complete, resulting in a left atrial "rupture". The most common locations for a left atrial split were reported to be the atrial free wall, but an interatrial septal rift could occur as well, typically at the level of the fossa ovalis - the thinnest portion of the atrial septum. Reports of left atrial splits, tears, or rupture (terminology varies) are very rare in the veterinary literature. A small case series of 14 cases of pericardial effusion secondary to a left atrial rupture described in 2008 (Reinecke et al., JVECC 2008) reported a very poor prognosis, with only four dogs surviving over 35 days. This study described patients before the availability of pimobendan. A second retrospective of 11 dogs with free wall atrial tears, published in 2014, reported survival to discharge in 10 dogs, and median survival of those discharged of 345 days in patients with no history of CHF and 160 days in patients with a history of CHF (Nakamura et al.,  JAAHA 2014). A point was made that the patients in the study were stable enough to undergo echocardiography. Therefore, they survived to hospital admission, and to undergo further diagnostics. Other patients may not have been as lucky.

We reviewed the medical records of small dogs diagnosed with PCE and no obvious cardiac mass at The COVE since its opening in 2012. All the dogs were evaluated by Dr. Small (DACVIM Cardiology), Dr. Smith (DACVECC), or Dr. Nobles (DACVECC). The results were as follows: 
  • 56 dogs showed evidence of advanced myxomatous mitral valve disease, pericardial effusion, and no evidence of cardiac neoplasia.
  • 17 dogs had convincing echocardiographic evidence of a left atrial free wall rupture. 
  • 7 dogs had convincing echocardiographic evidence of an interatrial septal rupture. 
  • 4 dogs had evidence of both left atrial free wall rupture and interatrial septal tear, not necessarily at the same visit. 
  • 28 dogs had severe left heart enlargement and pericardial effusion without solid echocardiographic criteria of a recent left atrial tear, leading to a conclusion of possible/likely LA tear but ruling out atypical CHF.
Survival data was analyzed. Survival times ranged from 0 days to 44 months. Only six dogs expired within the first 48 hours of diagnosis. The mean survival in dogs with confirmed thrombi was 5.93 months; with PCE and no confirmed thrombus, 8.61 months; with interatrial tear, 5.68 months; and with both PCE and interatrial tear, 9 months.

In conclusion, left atrial rupture and/or pericardial effusion associated with advanced mitral valve disease is very likely more common than reported in patients with advanced mitral valve disease. Patients can present acutely or chronically, but if the patient survives to presentation, the prognosis of survival to discharge is good, with a chance of survival of months to many months thereafter.

TECH TIP:  Monitoring the Cardiac Patient at Home
By Andi D., LVT
There is no substitute for a cardiac recheck with Dr. Small, but there are some modalities available that enable us to check in on how our cardiac patients are doing away from the hospital while allowing owners to keep tabs on how their pets are doing in their usual environment.  These provide us with an idea of how our patients are behaving in their homes when they aren't stressed by car rides or surrounded by doctors and medical equipment.
 
Respiratory Rates
Counting respiratory rates is one of the easiest ways owners can monitor their pets at home for possible changes in cardiac status, and it's also one of the most important tools at our disposal.  Very minimal equipment and time are required, and the results provide a lot of information, especially when daily rates are obtained for comparison.  A timer is set for 15 or 30 seconds, and the number of breaths in that time; the result is then multiplied by 4 or 2, respectively, to obtain a rate/minute. Ideally, we like to see a rate below 40bpm; anything at 40bpm or higher necessitates a phone call for medication adjustments or a trip in for evaluation.  Whether owners keep track via a printed table or utilize the Cardalis app (free of charge) on their smartphone device, they can quickly observe changes from baseline and track their pet's progress on a daily basis.
 
Heart Rates
We can, and certainly do, monitor heart rates and check for arrhythmias while patients are in the hospital, but the most ideal environment to do so is at home where they are relaxed and surrounded by their family and normal routine. Luckily, we have monitoring capabilities that owners can utilize at home in order to capture the most accurate information.
 
For animals that have been diagnosed with atrial fibrillation, the goal of medical therapy is to get their heart rates down into a target range of 120-130bpm. Without at-home monitoring, this requires weekly visits to get an ECG at the hospital, where we know their heart rates are going to be higher due to stress and travel.  However, now we can send owners home with the portable Kardia device so they can obtain an ECG at any time.  The Kardia is placed either on the front paws (most comfortable for cats) or along the side of the chest (best for dogs), and the signal is transmitted to the owner's smartphone with either the Kardia (Droid) or Alivecor ECG (Apple) apps. The ECG is recorded and e-mailed directly to the Cardiology Team as a PDF for review.  The pets usually tolerate this very well, and only about 15-45 seconds of time are required for the test.  As many ECGs as desired can be recorded and sent by the owners, and medication changes can be made without those stressful weekly trips to and from the hospital.  Best of all, these ECGs can be obtained at any time - day or night - and the Cardio Team can access the PDFs within minutes to check for suspicious rhythms or sudden increases in heart rate.
 
For animals with a suspected or diagnosed arrhythmia, the most important information to determine is the frequency of the arrhythmia.  We're able to document this via a Holter monitor: a cell phone-sized device worn in a pocket on a neoprene vest for 24-72 hours.  The pet (yes, cats get to participate, too!) is able to engage in all of its normal activities (with the exception of baths and swimming), and the Holter records a continuous ECG for the selected time period.  The data is then downloaded and submitted to NC State for analysis before being completely reviewed by Dr. Small.  This provides a much more accurate assessment than just a snapshot visit to the hospital, and it's the most accurate method for assessing effectiveness of anti-arrhythmic medications.
 
Many thanks to our "models" for their assistance: Smaug Gustafson, Sari Swersky, Nala Edelson, and Bella Kibler.
DID YOU KNOW? 

Genetic Studies Are Available
The COVE Cardiology Team is participating in a few genetic studies conducted by NC State with the goal of identifying genetic markers for several common cardiac diseases: mitral valve endocardiosis in Cavalier King Charles Spaniels, tricuspid valve dysplasia in Labrador Retrievers, and dilated cardiomyopathy in Great Danes. All that is required is a sample of EDTA blood and, ideally (if known), the pedigree of the affected animal. We can supply the copies of the most recent echocardiogram and submit the samples to NC State's Genetics Lab. The lab is also collecting samples from healthy dogs confirmed to be free of heart disease, but they must meet the following age criteria:
  • Cavaliers must be at least 10 years old
  • Great Danes must be at least 9 years old
If clients are coming in for a regular appointment, we will be in touch with them the day before to speak about the study and to ask them to bring their dog's pedigree. If you are interested in having a healthy dog participate, please feel free to get in touch with us, or visit the  NC State Genetics Lab website. 

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Nutritional Dilated Cardiomyopathy
Since the FDA's announcement regarding a possible link between grain-free diets and dilated cardiomyopathy, the Cardiology Team has been documenting all our cases of suspected nutritional dilated cardiomyopathy. Many of these cases have also been submitted to the  FDA's Safety Reporting Portal to help narrow down the causal agents. We have also developed a brochure to help educate our clients on the dangers of these "BEG" (boutique, exotic, and grain-free) diets, providing them with links to the FDA announcements and nutritional resources to give them as much information as possible.


Happy 7th Anniversary to The COVE!

This spring, we celebrated our 7th anniversary providing specialty and 24/7 emergency care. You, our referring community, along with our amazing team, have made this milestone possible. Thank you for your continued support. To highlight a few memorable cases we've seen over the years, check out late May's Downtowner cover story.
Tracheal Stent Placement

Dr. Nobles placed our first tracheal stent at the COVE recently via bronchoscopy and radiography. The patient is doing very well. The procedure was not only life saving, but life enhancing. This is just one example of the great success we've had with our  minimally invasive surgery capabilities . Stay tuned for a detailed case study coming soon.  
Conference - Bound!

We attended the industry conference  ACVIM in Phoenix  in June where The COVE's Marie Moore, LVT, AS, presented a case report during the Technician Track. We are happy to report that she was selected as a finalist amongst all those that presented case reports. We will be attending  IVECCS in Washington, D.C.  in September. Hospital Manager Danielle Russ, LVT, BS, BA, AS will be speaking at the Veterinary Hospital Managers Association  meeting in Glendale, AZ  in September. Be sure to stop by and say hello if you're attending!

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