Systolic heart murmur in a 1-year-old cat

Claudia Serrano Ferrel College of Veterinary Medicine, Auburn University, Auburn, AL

Search for other papers by Claudia Serrano Ferrel in
Current site
Google Scholar
PubMed
Close
 MS, DVM
,
Randolph L. Winter College of Veterinary Medicine, Auburn University, Auburn, AL

Search for other papers by Randolph L. Winter in
Current site
Google Scholar
PubMed
Close
 DVM, PhD, DACVIM
,
Brad M. Matz College of Veterinary Medicine, Auburn University, Auburn, AL

Search for other papers by Brad M. Matz in
Current site
Google Scholar
PubMed
Close
 DVM, MS, DACVS
,
Kara L. Maneval College of Veterinary Medicine, Auburn University, Auburn, AL

Search for other papers by Kara L. Maneval in
Current site
Google Scholar
PubMed
Close
 DVM
,
Katherine Gerken College of Veterinary Medicine, Auburn University, Auburn, AL

Search for other papers by Katherine Gerken in
Current site
Google Scholar
PubMed
Close
 DVM, MS, DACVECC
, and
Rachel S. Moon College of Veterinary Medicine, Auburn University, Auburn, AL

Search for other papers by Rachel S. Moon in
Current site
Google Scholar
PubMed
Close
 DVM, DACVR

Click on author name to view affiliation information

History

A 1-year-old 2.3-kg sexually intact female domestic shorthair cat was presented to the Auburn University College of Veterinary Medicine for evaluation of a heart murmur. The cat was presented to its referring veterinarian 3 months prior for an episode of respiratory distress. At that time, a grade 2/6 systolic heart murmur was auscultated over the right cranial aspect of the thorax. No medications were prescribed, but referral for further evaluation was made. At the Auburn University Veterinary Teaching Hospital, thoracic auscultation revealed a grade 4/6 systolic, right parasternal heart murmur. Mild tachycardia (240 beats/min; reference range, 120 to 220 beats/min) and tachypnea (50 breaths/min; reference range, 16 to 40 breaths/min) were observed. The remainder of the physical examination findings were unremarkable. Thoracic radiography was performed (Figure 1).

Figure 1
Figure 1
Figure 1

Right lateral (A) and ventrodorsal (B) thoracic radiographic images of a 1-year-old 2.3-kg sexually intact female domestic shorthair cat presented for further evaluation of a heart murmur and tachypnea.

Citation: Journal of the American Veterinary Medical Association 261, 11; 10.2460/javma.23.06.0333

Diagnostic Imaging Findings and Interpretation

Thoracic radiography revealed severe cardiomegaly with no apparent pulmonary parenchymal pathology. No abnormalities of the pleural space, mediastinum, or diaphragm were observed. Pulmonary overcirculation was evident, as enlarged pulmonary arteries and veins were observed (Figure 2). Peripheral pulmonary arteries were also subjectively tortuous. A focal bulge of the main pulmonary artery was present. Based on the patient’s age and the findings of pulmonary overcirculation, tortuous pulmonary arteries, and main pulmonary arterial enlargement, a congenital cardiac defect with subsequent development of pulmonary hypertension was considered likely. Differential diagnoses included an atrial septal defect, ventricular septal defect, and a patent ductus arteriosus (PDA).

Figure 2
Figure 2

Same radiographic images as Figure 1. Generalized cardiomegaly is apparent on both views. A—The pulmonary parenchyma is radiographically normal, and pulmonary overcirculation is noted with enlarged and tortuous pulmonary arteries and veins (arrows). B—There is a focal bulge (arrow) in the region of the main pulmonary artery.

Citation: Journal of the American Veterinary Medical Association 261, 11; 10.2460/javma.23.06.0333

Transthoracic echocardiography revealed mild to moderate dilation of the left ventricle, severe concentric hypertrophy of the right ventricle, and severe dilation of the main pulmonary artery. There was moderate tricuspid regurgitation, the velocities of which suggested severe pulmonary hypertension. An intracardiac shunt was not observed by 2-D imaging (Supplementary Video S1), color-flow Doppler echocardiography, or an agitated saline microbubble study. An abnormal color-flow Doppler echocardiographic signal was observed in the main pulmonary artery during systole, but a left-to-right, continuously shunting PDA was not observed (Supplementary Video S2). The following day, the patient underwent general anesthesia and selective angiography. Enlarged and tortuous pulmonary arteries were observed. Utilizing selective angiography of the right ventricular outflow tract and the descending aorta, a large, bidirectionally shunting PDA was also observed (Figure 3; Supplementary Video S3). During the echocardiogram, a single-lead ECG was performed, which demonstrated sinus tachycardia.

Figure 3
Figure 3

Left lateral angiographic view of the heart of the cat described in Figure 1, with the patient’s head to the right in these images. A—An angiographic catheter is positioned through the jugular vein into the right ventricular outflow tract (tip of the catheter notated by arrowhead). Selective angiography reveals a severely enlarged and tortuous left pulmonary artery (LPA) and right pulmonary artery (RPA) and flow through a patent ductus arteriosus (asterisk) into the aorta. B—The catheter tip (arrowhead) is positioned through the patent ductus arteriosus into the descending aorta. Selective angiography reveals blood moving primarily from the aorta into the main pulmonary artery through a large patent ductus arteriosus (asterisk).

Citation: Journal of the American Veterinary Medical Association 261, 11; 10.2460/javma.23.06.0333

Treatment and Outcome

The size and shape of the patent ductus arteriosus, having a large diameter (6.3 mm) and a length of 10.3 mm, precluded occlusion of the PDA with an occlusion device. The patient was recovered from anesthesia, and ligation of the PDA via a standard lateral thoracotomy was performed 2 days later. The patient recovered uneventfully from anesthesia. A residual amount of ductal flow was observed on transthoracic echocardiography 1 day after the thoracotomy, but a decrease in left ventricular diameter was observed compared with the preoperative images. Sildenafil (2.0 mg/kg, PO, q 12 h) was initiated, and the patient was discharged. Recheck examinations were performed 3 and 6 months later. Progressive decrease in the left ventricular diameter was observed, ultimately resulting in a normal left ventricular diameter. The concentric hypertrophy of the right ventricle decreased slightly but remained moderately hypertrophied. The main pulmonary artery enlargement and mild residual ductal flow remained. No clinical signs had been reported in this patient at the time of writing (8 months postoperatively).

Comments

Pulmonary overcirculation describes the enlargement of peripheral pulmonary arteries and pulmonary veins concurrently.1 This finding is in contrast to primary pulmonary hypertension, which is likely to have pulmonary arterial enlargement but normal pulmonary venous size, and a left heart volume overload, which is likely to have pulmonary venous enlargement but not necessarily pulmonary arterial enlargement.1 Pulmonary overcirculation is a common finding in dogs. Typically, a prominent pulmonary overcirculation pattern is observed when there is substantial volume overload present. The cat of this report had severe cardiomegaly observed radiographically, and transthoracic echocardiography revealed moderate dilation of the left ventricle. This is in keeping with the left-to-right shunting aspect of this bidirectionally shunting PDA. Left ventricular dilation and pulmonary overcirculation have also been described in cats with PDAs.2 The left ventricular dilation resolved after surgical ligation in this patient.

Radiographic signs of pulmonary hypertension were observed in this patient, including tortuous pulmonary arteries and main pulmonary artery enlargement. These findings were also observed via transthoracic echocardiography and selective angiography. It is important to remember that these signs are not pathognomonic for any 1 specific disease and are observed in both congenital and acquired diseases.1 Observation of a main pulmonary artery bulge on thoracic radiography can be observed in animals with a left-to-right shunting PDA and normal pulmonary arterial pressures, but transthoracic echocardiography helped confirm the presence of pulmonary hypertension in this patient. Transthoracic echocardiography revealed severe concentric hypertrophy of the right ventricle, which is observed in patients with pulmonary hypertension. Additionally, measurement of the tricuspid regurgitant velocities also suggested severe pulmonary hypertension, with a systolic pulmonary arterial pressure estimated at 100 mm Hg.

The combination of severe pulmonary hypertension and pulmonary overcirculation in a young cat suggested the presence of a congenital left-to-right shunt. Ventricular septal defects are common congenital cardiac defects in the cat, whereas PDAs are rarer by comparison.3 Transthoracic echocardiography was instrumental in ruling out an atrial or ventricular septal defect, both of which could have caused pulmonary overcirculation and subsequent pulmonary hypertension. Diagnosis of a left-to-right shunting PDA is often straightforward with thoracic auscultation and transthoracic echocardiography; however, the concurrent presence of severe pulmonary hypertension and the bidirectional shunting nature of this PDA complicated the diagnosis. Cats with PDAs have been described as having radiographic evidence of pulmonary overcirculation with left-to-right, bidirectional, and even right-to-left shunting.2 Selective angiography was utilized in this case, but CT has also proven useful in similar cases.4,5 Advanced imaging such as CT angiography or cardiac MRI may be used to aid in disease diagnosis,5 and these may be of particular importance if tests such as echocardiography fail to provide a complete understanding of the disease diagnosis. These imaging modalities were not needed in the case reported here. Finding pulmonary overcirculation and radiographic signs of pulmonary hypertension, such as pulmonary arterial tortuosity and main pulmonary artery enlargement, should suggest the possible presence of a PDA in a cat even in the absence of physical examination abnormalities such as a continuous heart murmur.

Supplementary Materials

Supplementary materials are posted online at the journal website: avmajournals.avma.org

Acknowledgments

The authors thank Silas Zee for assistance with figures.

Disclosures

The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.

Funding

The authors have nothing to disclose.

References

  • 1.

    Lord P, Suter PF. Radiology. In: Textbook of Canine and Feline Cardiology. 2nd ed. WB Saunders Co; 1999:107-129.

  • 2.

    Bascuñán A, Thieman Mankin KM, Saunders AB, et al. Patent ductus arteriosus in cats (Felis catus): 50 cases (2000-2015). J Vet Cardiol. 2017;19(1):35-43. doi:10.1016/j.jvc.2016.10.002

    • Search Google Scholar
    • Export Citation
  • 3.

    Schrope DP. Prevalence of congenital heart disease in 76,301 mixed-breed dogs and 57,025 mixed-breed cats. J Vet Cardiol. 2015;17(3):192-202. doi:10.1016/j.jvc.2015.06.001

    • Search Google Scholar
    • Export Citation
  • 4.

    Saunders AB, Birch SA. Three-dimensional modeling of a patent ductus arteriosus in a cat. J Vet Cardiol. 2015;17(suppl 1):S349-S353. doi:10.1016/j.jvc.2015.08.006

    • Search Google Scholar
    • Export Citation
  • 5.

    Karn M, Potter BM, Pierce KV, Scansen BA. Medial insertion of the patent ductus arteriosus characterized by computed tomography angiography in a cat and dog. J Vet Cardiol. 2022;41:145-153. doi:10.1016/j.jvc.2022.02.003

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 1456 1312 0
Full Text Views 666 657 51
PDF Downloads 585 570 64
Advertisement