Page 293 - Clinical Small Animal Internal Medicine

26 Canine Myocardial Disease 261

in addition to delay in disease progression and prolon- sinus rhythm may be physiologically ideal, rate control is
VetBooks.ir gation of survival. Strategies include intravascular vol- much more feasible. Evidence suggests that the combina-
tion of diltiazem with digoxin is more efficacious for rate
ume reduction to resolve pulmonary edema or decrease
cavitary effusions, improvement in hemodynamic
<125 bpm on Holter recording is ideal, and given higher
performance through decreased systemic vascular control than either drug alone. A target mean HR
resistance and improved contractility, neurohumoral HR in hospital, target mean HR on in‐hospital ECG
modulation, arrhythmia management, and nutritional should be <140–150 bpm. Alternative therapy choices
management. include a beta‐blocker or sotalol, though beta‐blockers
The mainstay of treatment of edema and effusions should not be initiated in the setting of acute or poorly
remains diuretics, with furosemide the most commonly managed heart failure.
used agent. It may be administered orally or intrave- Cardiac cachexia is identified commonly in DCM CHF
nously depending on the severity of CHF and whether patients and nutritional support is an important part of
the patient is being treated as an inpatient or outpatient. therapy. Due to anorexia, increased energy require-
Following edema resolution, the dose may be lowered to ments, and production of inflammatory cytokines, lean
the effective dose that maintains the patient free of muscle mass is lost in the chronic heart failure patient.
respiratory signs and edema. Given its relatively short Management involves providing adequate calories and
duration of action, dosing more than twice daily may be protein, and there is evidence that supplementation with
more effective. Substantive pleural effusion or ascites omega‐3 fatty acids is beneficial. While diets restricted
should be relieved with thoraco‐ and abdominocentesis, in sodium are commonly advocated, the effects on qual-
respectively. ity of life or survival have not been assessed in dogs.
Angiotensin converting enzyme inhibitor is indicated
for RAAS blockade and vasodilatory effects, particularly Overt DCM – Severe Life‐Threatening CHF
in the setting of furosemide use which heightens RAAS Parenteral means of decreasing intravascular volume,
stimulation. The results of veterinary clinical trials using increasing contractility, decreasing vascular resistance,
enalapril and benazepril report improved quality of life, and treating arrhythmias may be necessary in cases of
and although the improvements in survival did not reach severe CHF. Administration of oxygen by nasal prongs,
statistical significance for DCM dogs, there is clear cannula or cage is indicated in the case of hypoxia.
evidence of mortality reduction in human patients and Administration of intravenous (IV) furosemide by bolus
ACEI use is considered standard therapy in dogs with or constant rate infusion (CRI) is the single most impor-
DCM and CHF. tant and effective strategy to initiate promptly. Multiple
Three placebo‐controlled trials have found signifi- boluses may be administered 30–60 minutes apart until
cantly longer time to treatment failure or longer survival the respiratory rate drops 50% from initial presentation
time in DCM dogs treated with pimobendan in addition or effort improves. If there is inadequate response after
to diuretics and ACEI, so pimobendan is considered part three doses, CRI should be initiated. Alternatively, one
of standard therapy for CHF due to DCM. bolus followed immediately by CRI is preferred if the
The aldosterone antagonist spironolactone signifi- patient has preexisting azotemia or is particularly severe.
cantly reduces morbidity and mortality in humans with Careful monitoring of volume status, renal function, and
CHF and LV systolic dysfunction. While similar evidence electrolytes is required. Thoracocentesis is indicated if
is lacking in dogs with DCM, a study in Dobermans with substantive pleural effusion is contributing to dyspnea.
CHF suggested a reduced risk of AF with spironolactone If rapid AF is present, initiation of IV diltiazem is indi-
therapy. Spironolactone is often used in the patient that cated to reduce HR below 140–150 bpm. In cases of VA
is still symptomatic despite use of triple therapy with in the setting of CHF, treatment may be warranted if VT
furosemide, ACEI, and pimobendan, whereas some, is present, signs of weakness or collapse are present, or
including the author, advocate using it initially as part of the patient is a breed with a high incidence of SD such as
standard therapy. Spironolactone is licensed for use in Dobermans and boxers. IV lidocaine is typically the first
dogs with CHF in Europe. treatment of choice.
Management of the overt DCM patient with VA In the absence of arrhythmias, IV furosemide may be
includes optimal management of congestion and hemo- enough to stabilize some patients whereas others will
dynamics to reduce sympathetic nervous system stimu- require the addition of a parenteral positive inotrope +/−
lation and improve perfusion. Specific AA therapy may vasodilator. Dobutamine CRI is the IV positive inotrope
also be indicated. Patients with VA may be managed as of choice for treatment of severe edema and hypoten-
outlined above for the preclinical stage. DCM patients sion. Side‐effects include nausea/vomiting and exacerba-
with AF and in‐hospital HR >150 bpm are candidates for tion of VA, in which case the dose should be decreased.
rate control with AA therapy. While cardioversion to It is important to note that if AF is present, IV diltiazem