Direct HR: 140
Heart rhythm:  Regular
Intensity of heart sound: Heart sounds audible, but reduced
Extra sounds – clicks or gallops: None
Precordial palpation: No thrill detected

The CEG considers the following differential diagnosis as most likely (and why):CHF secondary to chronic valvular disease (CVD) is the most likely underlying etiology of the clinical signs because Riley is a small (<20Kg) older dog with a loud heart murmur characteristic of mitral regurgitation (MR). Dilated cardiomyopathy (DCM) cannot be ruled out but would be very unlikely in a Shih Tzu. CHF secondary to heartworm (HW) disease is less likely because of the history of heartworm prevenative, but should be considered in endemic areas especially if dogs are not on preventative. Pericardial effusion with tamponade is less likely because his heart sounds (murmur) are loud.

The CEG considers the following diagnostic tests as the highest priority:Thoracic radiographs must be considered as the most important diagnostic test in a patient with respiratory signs suspected of having congestive heart failure. An echocardiogram should be performed to confirm that there is enough underlying heart disease present to make the clinical signs likely to be attributable to heart failure. In addition, an echocardiogram is the definitive diagnostic test to document the presence of pericardial effusion, pulmonary hypertension and severe heartworm disease. Obtaining a serum chemistry is also important in this case, as the owner complained that Riley’s appetite has suffered after starting the cardiac therapy. Impairment of renal function and resulting azotemia is an important cause of decreased appetite in patients receiving therapy for CHF. Similarly, a blood pressure evaluation is important to rule out systemic hypertension and to identify adverse effects of current therapy. This is especially important if additional therapy is contemplated. An ECG should be obtained in any patient where an arrhythmia is identified/suspected (Riley had premature beats detected on auscultation). NT-proBNP is less useful if significant heart disease has been identified by echo; however this may be a very useful test if an echocardiogram cannot be obtained. A heartworm test can also be considered in a patient presented with signs of heart disease and right-sided heart failure; while still appropriate in this case, it may be less important given the rest of the case history. Evaluation of the abdomen (e.g. use of ultrasound, radiographs and/or fluid analysis) can also be considered, but would be most important if significant heart disease is not identified. In some cases, abdominal evaluation may be more important, especially if an acute abdomen (hemoabdomen, peritonitis, etc.) is suspected based on clinical findings. Similarly, a complete blood count can be considered a higher priority if infection/bleeding is a concern.

Technical quality: Good
Pulmonary venous congestion: No pulmonary venous congestion seen
Pulmonary infiltrate: No convincing interstitial changes are seen on the VD. Increased opacity is seen on the lateral, but may be due to the expiratory nature of the film.
Other findings: Loss of serosal detail is noted on the abdominal portion of the film.

THE CEG RECOMMENDS:
Riley has been diagnosed with Stage C Myxomatous valvular degeneration with concurrent, severe pulmonary hypertension. The CEG recommends therapy with sildenafil to address the pulmonary hypertension, as well as pimobendan and furosemide to relieve the signs of congestive heart failure. An ACE-inhibitor and spironolactone are also helpful adjuncts to help suppress the renin-angiotensin-aldosterone system and control signs of congestive heart failure.

ACTUAL TREATMENT:
Initial therapy-

Sotalol is a class III anti-arrhythmic drug that is useful in treating life-threatening or clinically important ventricular and supraventricular arrhythmias in dogs. Riley does not currently have evidence of important or life-threatening arrhythmias, and disease and pulmonary hypertension. Although sotalol may be helpful in the future, it is not currently indicated.

Pimobendan 1.25 mg: 1 tablet every 12 hours.
Based on ACVIM Consensus statement guidelines, pimobendan is indicated in patients with congestive heart failure secondary to myxomatous valvular degeneration (Stages B2, C, and D). Pimobendan is also a phosphodiesterase III inhibitor with some vasodilatory properties that also affect the pulmonary vasculature.

Digoxin is a positive inotropic agent with negative chronotropic properties and may be indicated for adjunctive therapy in refractory congestive heart failure or in the management of tachyarrhythmias. However, it is a relatively weak positive inotropic agent relative to pimobendan and has a narrow therapeutic window, making it more difficult to use. Although it may be useful for Riley in the future, it is not considered first-line therapy for Riley that should be initiated at this time.

Continue spironolactone 25mg: ¼ tablet every 12 hours.
Based on ACVIM consensus statement guidelines, pimobendan is indicated in patients with clinically important mitral regurgitation and congestive heart failure secondary to myxomatous valvular degeneration (Stages C and D). Care should be taken to monitor renal function in patients already receiving diuretics if this medication is added to the treatment plan.

Sildenafil 20mg tablets: ¼ tablet every 8 hours.
Sildenafil is a phosphodiesterase V inhibitor with vasodilatory properties that is relatively selective for the pulmonary vasculature. Based on ACVIM Consensus statement guidelines, sildenafil is indicated in the management of patients with severe pulmonary hypertension such as Riley.

Benazepril. Based on ACVIM Consensus statement guidelines, an ACE-inhibitor is indicated in patients with congestive heart failure secondary to myxomatous valvular degeneration (Stages C and D). Care should be taken to monitor renal function in patients already receiving diuretics if this medication is added to the treatment plan.

Amlodipine is a calcium channel blocker with vasodilator properties that is useful in the management of systemic hypertension in dogs and cats. Although it also may cause some dilation of pulmonary arteries, this effect is much less pronounced than its effect on systemic arteries or the effects of sildenafil.

Continue furosemide 12.5 mg: 1 tablet every 12 hours.

Continue enalapril 2.5mg: 1 tablet every 12 hours.

Follow-up plan:
1. Recheck examination in 7-14 days.

• • Physical examination and weight
  • Renal profile with electrolytes
  • Echocardiogram to assess pulmonary pressures via tricuspid regurgitation velocities
  • Adjust diuretic therapy as necessary for persistent ascites
  • Palliative abdominocentesis if clinically important ascites that is non-responsive to diuretics (or in patients that cannot tolerate escalating diuretic therapy)

2. Lifestyle adjustments:

• • Avoid high sodium treats and foods such as processed meats, hot dogs, cheese, some table scraps. If Riley is eating well, encourage transition to a prescription low-sodium diet.
  • Avoid stress or strenuous exertion

3. Long-term: Recheck every 3-4 months or as needed for symptoms or recurrent heart failure, syncope, or other signs of deteriorating quality of life.