A 10-month-old 4.62-kg (10.16-lb) neutered male domestic longhair cat was evaluated because of acute lethargy and labored breathing. The cat had been previously healthy with no notable medical history.
Physical examination findings revealed the cat had a dull mentation, but it was responsive. Rectal temperature was 37.7°C (99.8°F). Cardiac auscultation revealed a heart rate > 300 beats/min with a regular rhythm and no murmur or gallop sound. The femoral pulse quality was weak. The cat was tachypneic with a respiratory rate of 60 breaths/min and mild respiratory effort. Lung auscultation revealed harsh lung sounds. Thoracic radiography was performed, and the images were reviewed by a board-certified veterinary radiologist; findings included mild cardiomegaly and mild diffuse bronchial pattern, but there was no evidence of congestive heart failure.
The cat underwent echocardiography, which revealed severe left ventricular concentric hypertrophy (in a 2-D long-axis view, the left ventricular posterior wall thickness in diastole was 0.8 cm [reference interval,1 0.31 to 0.41 cm] and interventricular septal wall thickness in diastole was 0.6 cm [reference interval,1 0.29 to 0.39 cm]) and marked left atrial and moderate left auricular dilation (left atrial-to-aortic root diameter ratio, 3.00; reference interval,1 1.13 to 1.68). The left ventricle appeared volume underloaded, and systolic function appeared adequate despite the severe tachyarrhythmia. The suspected diagnosis was juvenile-onset hypertrophic cardiomyopathy (HCM). Transient myocardial thickening was considered; however, there was no antecedent event identified, and severe cardiac remodeling and concomitant arrhythmias in association with that disease entity in cats have not previously been reported.2 Given the cat's young age, left ventricular hypertrophy secondary to hyperthyroidism, acromegaly, or systemic hypertension was considered unlikely. Electrocardiography was performed.
2. Novo Matos J, Pereira N, Glaus T, et al. Transient myocardial thickening in cats associated with heart failure. J Vet Intern Med 2018;32:48–56.
3. Tilley LP, Smith FWK Jr. Electrocardiography. In: Tilley LP, Smith FWK Jr, Oyama MA, et al. Manual of canine and feline cardiology. 4th ed. St Louis: WB Saunders, 2008;270–274.
4. Ferasin L, Sturgess CP, Cannon MJ, et al. Feline idiopathic cardiomyopathy: a retrospective study of 106 cats (1994–2001). J Feline Med Surg 2003;5:151–159.
5. Boyden PA, Tilley LP, Albala A, et al. Mechanisms for atrial arrhythmias associated with cardiomyopathy: a study of feline hearts with primary myocardial disease. Circulation 1984;69:1036–1047.
6. Santilli RA, Perego M, Crosara S, et al. Utility of 12-lead electrocardiogram for differentiating paroxysmal supraventricular tachycardia in dogs. J Vet Intern Med 2008;22:915–923.
7. Ferasin L. Recurrent syncope associated with paroxysmal supraventricular tachycardia in a Devon Rex cat diagnosed by implantable loop recorder. J Feline Med Surg 2009;11:149–152.
9. Neiger JS, Trohman RG. Differential diagnosis of tachycardia with a typical left bundle branch block. World J Cardiol 2011;3:127–134.
10. Alraies MC, Eisa N, Alraiyes AH, et al. The long and short of it: Ashman's phenomenon. Am J Med 2013;126:962–963.
11. Johnson MS, Martin M, Smith P. Cardioversion of supraventricular tachycardia using lidocaine in five dogs. J Vet Intern Med 2006;20:272–276.
12. Hebbar AK, Hueston WJ. Management of common arrhythmias: part I. Supraventricular arrhythmias. Am Fam Physician 2002;65:2479–2486.
13. Epstein AE, DiMarco JP, Ellenbogen KA, et al. 2012 ACCF/AHA/HRF focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities. J Am Coll Cardiol 2013;61:e6–e75.
14. Gordon SG, Cote E. Pharmacotherapy of feline cardiomyopathy: chronic management of heart failure. J Vet Cardiol 2015;17:S159–S172.
15. Payne JR, Borgeat K, Conolly DJ, et al. Prognostic indicators in cats with hypertrophic cardiomyopathy. J Vet Intern Med 2013;27:1427–1436.