Heart Failure: Clinical & Diagnostic Findings

Heart Failure: Clinical & Diagnostic Findings

• Heart failure is categorized into "forward" (output) failure and "backward" (congestive) failure
• "Forward" failure results from inadequate output, leading to symptoms like generalized weakness, depressed mentation, decreased exercise tolerance (especially in performance animals), syncope, hypotension, hypothermia, lactic acidosis, azotemia, and oliguria (due to inadequate tissue perfusion)
• "Backward" failure results from congestion, causing abnormal fluid accumulation. Left-sided failure can lead to interstitial pulmonary edema, while right-sided failure causes pleural and/or abdominal effusions, and peripheral tissue edema. Cats may also experience pulmonary edema, pleural effusion, or both in left-sided heart failure
• Most patients with heart failure exhibit a combination of "forward" and "backward" failure symptoms

Clinical Manifestations of Heart Failure

• Right-sided CHF: Visual signs of high right-sided filling pressures include jugular venous distension/pulsation and hepatojugular reflux in dogs. Abnormal fluid accumulation can manifest as abdominal distension (from liver enlargement or ascites), decreased/absent lung sounds from pleural effusion, and dependent peripheral edema (more common in horses)
• Left-sided CHF: Respiratory signs due to pulmonary edema include dyspnea, tachypnea, orthopnea, cough (exceptions for cats), expectoration of frothy fluid or blood-tinged fluid in nostrils (especially in horses), and fine inspiratory crackles. Cats might exhibit decreased/absent lung sounds due to pleural effusion

Clinical Diagnosis of CHF

• To confirm CHF, confirm the patient has heart disease severe enough to cause clinical signs, and clinical signs directly relate to the patient's heart disease (and not some other condition)
• Diagnostic tools include:
  • Echocardiography (cardiac ultrasound): assesses heart size/function, sidedness of disease, pleural and pericardial spaces, and potential cardiogenic edema/effusion.
  • Thoracic radiographs: provides a "big picture" view of the cardiac silhouette, lungs, great vessels, pleural space and evidence of fluid accumulation
  • Electrocardiography (ECG): checks heart rhythm & rate. Helpful if arrhythmia or tachycardia is present.
  • Circulating cardiac biomarkers (NT-proBNP): an ancillary test assessing possible cardiogenic respiratory issues.
• Thoracic radiographs are crucial in determining whether respiratory signs are due to heart failure. Patterns include left- or right-sided heart enlargement, pulmonary infiltrates, structured or unstructured interstitial/alveolar patterns, and presence of pleural or abdominal effusions.
• Radiographic patterns include normal pulmonary, interstitial (moderate or severe), and alveolar patterns, with corresponding alterations in the vascular margins and the appearance of air bronchograms.

Special Considerations

• If a patient is too unstable for radiographs or has unclear radiographic signs, further assessments may be required, such as B-mode (brightness) 2D echocardiography.
• If a patient has marked sinus arrhythmia or slow heart rate, CHF is considered unlikely, with the exception of cats with frequent bradycardia and hypothermia. Other indicators for possible CHF in cats include a gallop sound or a heart rate under 200 bpm.
• NT-proBNP can be used to distinguish between cardiogenic and non-cardiogenic dyspnea. Elevations indicate a higher likelihood of heart disease, although it isn't specific to any single condition and false positives are common. Sensitivity and specificity values for this test vary based on tested animal (cats and dogs) and the criteria used (clinical findings plus CXR/PE).