VETgirl December 2024 BEAT e-Magazine

QUARTERLY BEAT / DECEMBER 2024

CLINICAL SIGNS: Dogs with pericardial effusion often present with a history of vomiting within 24h of presentation, particularly with acute onset. In cases of sub-acute to chronic onset, owners may report vague symptoms such as “ain’t doing right”, weakness, exercise intolerance, lethargy, tachypnea, syncope, cough, abdominal enlargement, or muscle wasting. Clinical signs may vary based on the underlying cause, acuteness of effusion, and severity. Signs can include decreased breath sounds ventrally if pleural effusion is present, muffled or absent heart sounds, and signs of cardiogenic shock. Most affected cats and dogs exhibit signs of right-sided congestive failure, including pleural effusion, ascites, hepatomegaly, and jugular vein distension (with or without jugular pulses). DIAGNOSIS: In dogs with pericardial effusion, low voltage (<1 mV) QRS complexes are the most common ECG finding. Electrical alternans (i.e., variations in QRS complex or occasionally T-wave size) is less common but more specific to pericardial effusion. Some effusions may not cause any changes in the size of the ECG ventricular complex. ECG findings are neither sensitive nor specific. Thoracic radiographs are neither sensitive nor specific for diagnosing pericardial effusion, even if tamponade is present. The cardiac silhouette can sometimes appear normal or may take on a globoid shape on radiographs. In a study of dogs, 22% showed no enlargement of the cardiac silhouette, and 43% lacked a globoid heart despite having pericardial effusion and clinical signs of tamponade. Typical signs of pulmonary edema, such as increased pulmonary densities and distended pulmonary veins, are less likely. Pulmonary nodular changes may indicate metastatic disease. Emergency cardiac POCUS can quickly and accurately identify pericardial effusion with high sensitivity and specificity. Three windows can be used during cardiac POCUS to assess for pericardial effusion: 1) the subxiphoid window, 2) transthoracic right parasternal imaging with the probe situated directly over the heart (often considered the most challenging site for accurately confirming pericardial effusion), and 3) transthoracic imaging just caudal to the heart at the pericardio- diaphragmatic window. Based on the authors’ experiences, the subxiphoid and pericardio-diaphragmatic sites are the easiest for distinguishing between pericardial and pleural effusion. Cardiac POCUS is usually performed in the patient position that is most comfortable for the patient, and the least likely to cause decompensation, which is often in a sternal or standing position. Thus, cardiac POCUS is rarely performed in right lateral recumbency, and patient comfort and stability are prioritized over patient positioning.

1. SUBXIPHOID POCUS (FIG. 1) Place the ultrasound transducer at the subxiphoid position and advanced cranially, slightly under the xiphoid process, rocking the probe until it is nearly parallel to the spine (most often in long axis, but short axis views can also be obtained). The depth is adjusted to visualize both the pleural space and the heart. Fanning the transducer from left to right will aid in localizing the heart. If the left ventricular wall is seen and is continuous with the diaphragm and liver (termed “cardiac blending”), significant clinical pericardial effusion can be ruled out. If a “black ring” (indicating fluid) outlined by a bright white line (the pericardium) is observed around the ventricle (circumferential effusion), the presence of pericardial fluid is confirmed. It's crucial to differentiate pericardial from pleural fluid; from the subxiphoid window, pleural effusion will track along the diaphragm, forming triangular shapes and angles.

POCUS TO LIVE, LIVE TO POCUS: DIAGNOSING PERICARDIAL EFFUSION IN SECONDS!

SØREN BOYSEN AND SERGE CHALHOUB DVM, DACVECC DVM, DACVIM University of Calgary, Faculty of Veterinary Medicine

In this VETgirl Webinar “POCUS to LIVE, LIVE to POCUS: Diagnosing Pericardial Effusion in Seconds!“ on September 24, 2024, Dr. Søren Boysen, DACVECC and Dr. Serge Chalhoub, DACVIM review how to master the art of pericardial POCUS for rapid identification of pericardial effusion! In case you missed the webinar, watch it again HERE or read the cliff notes below!

pericarditis, trauma, left atrial rupture, systemic coagulopathy, congestive heart failure, chronic uremia, intrapericardial cysts, granulation tissue, chylopericardium, or iatrogenic cases. Prognosis varies and depends on the underlying cause as well as treatment options. Dogs with hemangiosarcoma have a guarded to poor prognosis (median survival of 1-4 months), while those with idiopathic pericardial effusion have a good prognosis (up to 4 years). Survival rates in dogs with heart-base tumors will vary; chemodectomas tend to grow slowly and rarely metastasize, with median survival times of 2 years following surgical pericardectomy. Pericardial effusion and tamponade sometimes mimic other life- threatening conditions, which makes rapid diagnosis necessary to improve patient outcome. Without immediate treatment, the mortality rate is 100% for patients exhibiting severe clinical signs. The risks associated with pericardiocentesis are relatively low and reduced further when using ultrasound. Pericardiocentesis should be performed when clinically warranted. With the increasing availability of ultrasound in everyday practice and advances in emergency point-of-care ultrasound (POCUS) by non-specialists, rapid confirmation and treatment of pericardial effusion is now achievable within minutes of presentation.

INTRODUCTION Cardiac tamponade, a result of pericardial effusion leading to intrapericardial pressure that exceeds right ventricular diastolic pressure, is relatively common in dogs with pericardial effusion but rare in cats. (The most common cause of pericardial effusion in cats is hypertrophic cardiomyopathy and this rarely causes clinically significant pericardial effusion). Rapid acute fluid accumulation, resulting from events such as hemorrhage, right atrial rupture or idiopathic causes, can lead to increased intrapericardial pressure despite minimal fluid volume. In contrast, slow fluid accumulations—often seen with idiopathic pericarditis—allows time for the pericardium to stretch, which means larger fluid volumes may be present. In both scenarios, progressive cardiac compression leads to decreased cardiac filling, reduced cardiac output, and lowered arterial blood pressure, potentially resulting in cardiogenic shock. Conditions frequently linked to pericardial effusion in dogs include neoplasia (40-70%) and idiopathic pericarditis (20- 60%); however, some idiopathic cases may be the result of neoplasia that was not detected at the time of assessment. Common cardiac and extracardiac cancers include right atrial hemangiosarcoma and heart-base tumors (e.g., chemodectoma and mesothelioma). Less common causes include infective

Figure 1: In dogs, this allows the operator to visualize the left ventricular free wall blending seamlessly with the diaphragm and liver in the absence of pericardial effusion. When pericardial effusion is present, it appears as fluid curving around the heart’s apex, creating a separation between the heart and the liver and diaphragm, outlined by the pericardium. Image courtesy of Dr. Jantina McMurray with permission.

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