Cardiac arrhythmias

Disturbances in the normal cardiac rhythm are commonly detected in dogs and cats during physical examination. Single premature supraventricular or ventricular complexes followed by a pause in the rhythm or paroxysms of tachycardia that terminate abruptly may be detected in a variety of cardiac or systemic disease conditions. The fast, irregular rhythm associated with atrial fibrillation often indicates marked underlying myocardial or valvular disease, whereas a slow, regular rhythm may suggest conduction system disease (e.g. atrioventricular block), electrolyte imbalances (e.g. hyperkalemia), or alterations in the autonomic nervous system. Although electrocardiography is required for definitive diagnosis of the rhythm disturbance, physical examination often provides the premise for performing an electrocardiographic examination.

EVALUATING THE ABDOMEN

Be sure to carefully palpate the kidneys of older cats with heart murmurs because of the relationship between renal disease, systemic hypertension, and the development of left ventricular concentric hypertrophy or outflow tract obstructions.

EVALUATING THE EXTREMITIES

Palpating the femoral pulses and extremities may help you detect rhythm disturbances, regional or generalized perfusion deficits, and occlusion of peripheral veins or lymphatics.³ A common misconception is that the strength and quality of the femoral pulse are merely determined by the systolic performance of the heart. Instead, the pulse amplitude and character have many determinants, including forward stroke volume, rate of ejection, distensibility of the vascular bed, systemic vascular resistance, and the pulse pressure (the difference between the systolic and diastolic arterial pressures).³

Weak pulses may be identified in cases of myocardial failure in which the left ventricle ejects a small stroke volume, the peripheral vascular resistance is high, and the pulse pressure is narrow.³ The combination of a weak and late to rise femoral pulse (pulsus parvus et tardus) and a left basilar, systolic, crescendo-decrescendo murmur is suggestive of moderate to severe subaortic stenosis. Widening of the pulse pressure subsequent to diastolic run-off in dogs with patent ductus arteriosus produces a bounding, or water-hammer, pulse. Other conditions associated with diastolic run-off and bounding pulses include aortic insufficiency and peripheral arteriovenous fistulas. Because systemic hypertension tends to represent an increase in both the systolic and diastolic arterial pressures, the femoral pulse amplitude and character remain normal. A palpable reduction in the femoral pulse quality during inspiration (pulsus paradoxus) is most commonly detected in patients with pericardial effusion and cardiac tamponade.

The absence of palpable femoral pulses, coolness of the affected limbs, muscular rigidity and pain, and pallor of the footpads or nails are suggestive of vascular obstruction.³ Systemic thromboembolism in cats is commonly associated with myocardial disease, while dogs may develop vascular obstruction subsequent to bacterial endocarditis or any condition that promotes hypercoagulability (e.g. hyperadrenocorticism, protein losing nephropathy, immune-mediated hemolytic anemia).

CONCLUSION

Good physical examination skills and an understanding of the pathophysiology associated with cardiac disease are vital to maintaining the health and well-being of our patients. A physical examination can provide an intelligent guide for recommending advanced diagnostic techniques, is a cost-effective method of making serial observations, and aids in the early detection of critical findings. Although electrocardiography, radiography, and echocardiography are required to confirm the disease process, assess its severity, and rule out concurrent cardiac conditions, these diagnostic modalities will never supplant the utility of observation, inspection, palpation, and cardiac auscultation.

Barret J. Bulmer, DVM, MS, DACVIM (cardiology)
Department of Clinical Sciences
College of Veterinary Medicine
Kansas State University
Manhattan, KS 66506

REFERENCES

1. Oh JK, Seward JB, Tajik AJ. Overview. In: The echo manual. 2nd Ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 1999;1-5.

2. Braunwald E. Physical examination of the heart and circulation. In: Zipes DP, Libby P, Bonow RO, et al, eds. Braunwald's heart disease: a textbook of cardiovascular medicine. 7th Ed. Philadelphia, Pa: Elsevier Saunders, 2005;77-106.