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Cardiovascular emergencies

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Abstract

Patients presenting with cardiovascular emergencies are often unstable and quick decisions are necessary. It is important to keep in mind the main causes of cardiovascular compromise in small animals. This chapter covers: emergency approach in cases suspected of cardiovascular disease, acute heart failure, pericardial effusion, cardiac arrhythmias and arterial thromboembolism.

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Figures

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6.3 U-SEE general approach in dogs with syncope/weakness. If all the previous tests are within normal limits, metabolic causes of syncope should be checked. Serum glucose ± fructosamine, haematocrit and electrolytes (sodium, potassium, chloride) ± basal cortisol should be measured to evaluate for hypoglycaemia, anaemia and suspicion of hypoadrenocorticism, respectively. Neurological causes of weakness/seizures should also be considered. CHF = congestive heart failure; DCM = dilated cardiomyopathy; ECG = electrocardiogram; ECHO = echocardiogram; LA = left atrium; LV = left ventricle; MMVD = myxomatous mitral valve disease; RA = right atrium; RV = right ventricle. These presentations are less common in cats. Causes for syncope/weakness in cats are detailed in Figure 6.1 .
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6.4 U-SEE approach in dogs with syncope/weakness and wide complex tachycardia. For details of recommended doses, see Figure 6.32 . Avoid if systolic dysfunction (hypokinetic left ventricle) evident on U-SEE echocardiography. Only use intravenous solutions without polysorbate 80, as this may cause anaphylatic reactions. See text for further details. ARVC = arrhythmogenic right ventricular cardiomyopathy; CRI = constant rate infusion; DCM = dilated cardiomyopathy; ECG = electrocardiogram; ECHO = echocardiogram; GDV = gastric dilatation–volvulus; SVT = supraventricular tachycardia; VTach = ventricular tachycardia. These presentations are less common in cats. Causes for syncope/weakness in cats are detailed in Figure 6.1 .
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6.5 U-SEE approach in dogs with syncope/weakness and narrow complex tachycardia. For details of recommended doses see Figure 6.32 . Avoid if systolic dysfunction (hypokinetic left ventricle) evident on U-SEE echocardiography. In advanced cases of myxomatous mitral valve disease, do not use beta-blockers. Use with caution in cats. Oral administration of one of these drugs is indicated to prevent recurrence of the arrhythmia. Only use intravenous solutions without polysorbate 80, as this may cause anaphylatic reactions. See text for further details. AT = atrial tachycardia; AVRT = atrioventricular reciprocating tachycardia; CHF = congestive heart failure; ECG = electrocardiogram; JT = junctional tachycardia; SVT = superventricular tachycardia; WHWT = West Highland White Terrier. These presentations are less common in cats. Causes for syncope/weakness in cats are detailed in Figure 6.1 .
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6.6 U-SEE approach in dogs with syncope/weakness and bradyarrhythmias or sinus rhythm. Administer 0.04 mg/kg atropine s.c. and repeat electrocardiogram (ECG) in 30 minutes. A positive response to atropine is considered to be resolution of the atrioventricular block and an increase in heart rate to >160 bpm. If all the previous tests are within normal limits, metabolic causes of syncope should be checked. Serum glucose ± fructosamine, haematocrit and electrolytes (sodium, potassium, chloride) ± basal cortisol should be measured to evaluate for hypoglycaemia, anaemia and suspicion of hypoadrenocorticism, respectively. Neurological causes of weakness/seizures should also be considered. ARVC = arrhythmogenic right ventricular cardiomyopathy; DCM = dilated cardiomyopathy; ECG = electrocardiogram; ECHO = echocardiogram; SSS = sick sinus syndrome; SVT = supraventricular tachycardia. These presentations are less common in cats. Causes for syncope/weakness in cats are detailed in Figure 6.1 .
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6.7 U-SEE approach in patients with dyspnoea/tachypnoea. It should be noted that it is rare for dogs in congestive heart failure (CHF) to present with isolated pleural effusion. When present, it is almost always associated with ascites in cases of right-sided CHF or with pericardial effusion in cases of cardiac tamponade. Ao = aorta; DCM = dilated cardiomyopathy; FIP = feline infectious peritonitis; HCM = hypertrophic cardiomyopathy; IVSd = interventricular septum in diastole; LA = left atrium; LV = left ventricle; LVFWd = left ventricular free wall in diastole; MMVD = myxomatous mitral valve disease; RA = right atrium; RCM = restrictive cardiomyopathy; RV = right ventricle; UCM = unclassified cardiomyopathy.
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6.8 U-SEE approach in patients with abdominal enlargement. CHF = congestive heart failure; ECG = electrocardiogram; RA = right atrium; RV = right ventricle.
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6.9 U-SEE approach in patients with paresis/paralysis. ATE = arterial thromboembolism; CK = creatine kinase; IMHA = immune-mediated haemolytic anaemia; LA = left atrium; UPC = urine protein:creatinine ratio.
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6.10 (a) Right parasternal long-axis four-chamber view in a normal dog at end-systole just before mitral valve opening. From this view it is possible to assess the atria, atrioventricular valves, ventricles and pericardial space. (b) Right parasternal short-axis view at the level of the heart base in a normal dog at end-systole before aortic valve opening (i.e. just after the T wave on the ECG). From this view it is possible to assess the left atrium (size, presence of ‘smoke’, thrombus) and pericardial space. Ao = aorta; LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle.
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6.11 Right parasternal long-axis four-chamber view in a cat with hypertrophic cardiomyopathy (obtained just before mitral valve opening). The atria can be assessed using this view. The measurement should be obtained parallel to the mitral or tricuspid valve annulus, dissecting the atrium into two equal parts. The cursor should be placed in the interatrial septum and a line drawn to the atrial free wall. In this case, the left atrium (LA) was measured and shown to be dilated at 24 mm (normal <16 mm).
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6.12 Right parasternal short-axis view at the level of the heart base in a dog with myxomatous mitral valve disease and severe left atrial dilatation. This view can be used to measure the dimension of the left atrium (LA) in both dogs and cats. In the first instance the aorta (Ao) should be measured by drawing a line from the commissure between the left coronary cusp and the non-coronary cusp to the middle of the right coronary cusp. In this case, it measured 12.21 mm. The LA size is measured by extending this line to the edge of the atrial free wall. In this case, the dimension of the LA measured 45.23 mm. The LA/Ao ratio was determined to be 3.70 (normal LA/Ao ratio is <1.6).
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6.13 Right parasternal long-axis four-chamber view in a dog with myxomatous mitral valve disease and rupture of a primary mitral valve chorda tendinea. In cases of major chordal rupture, the affected valve leaflet will display a chaotic ‘flailing’ movement and the ruptured chorda is displaced into the left atrium (LA) when the mitral valve closes in systole (arrowed). LV = left ventricle.
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6.14 Right parasternal long-axis four-chamber views in two cats with restrictive cardiomyopathy. (a) A large amount of spontaneous echocardiographic contrast is visible in the left atrium (LA). In real-time this is seen as ‘smoke’ (i.e. spontaneous echocardiographic contrast) swirling around the atrium. This is typically seen in severely dilated atria and is a marker of increased thromboembolic risk. (b) A large thrombus is seen inside the LA. LV = left ventricle; RA = right atrium.
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6.15 Left ventricular (LV) M-mode image acquired from a right parasternal short-axis view at the level of the papillary muscles in a dog with (a) myxomatous mitral valve disease and (b) dilated cardiomyopathy (DCM). These are two examples of LV eccentric hypertrophy but with marked differences in myocardial systolic function. Note the (a) hyperkinetic LV motion, which is typically associated with mitral regurgitation, and (b) the hypokinetic LV motion, which defines a DCM phenotype.
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6.16 Right parasternal long-axis four-chamber view in a cat with hypertrophic cardiomyopathy. There is severe ventricular hypertrophy (normal left ventricular wall thickness in diastole is <6 mm; in this case LV walls measured 8–9 mm). The left ventricular wall should be measured at end-diastole (just after mitral valve closure) and the thickest segments should be chosen for measurement. LA = left atrium; LV = left ventricle.
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6.17 Right parasternal short-axis view at the level of the papillary muscles in a dog with (a) severe tricuspid dysplasia and (b) pulmonic stenosis. (a) There is severe right ventricular eccentric hypertrophy associated with the tricuspid dysplasia. Note the tricuspid valve (arrowed) is visible in the middle of the right ventricle (RV). (b) There is severe right ventricular concentric hypertrophy associated with the pulmonic stenosis. LV = left ventricle.
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6.18 Right parasternal (a) long-axis four-chamber view and (b) short-axis view at the level of the papillary muscles in a dog with pericardial effusion. Pericardial effusion (PE) can be easily detected as a hypoechoic/anechoic region around the heart (between the epicardium and pericardium). In (a) note the collapse of the right atrium (RA; arrowed) indicating the presence of cardiac tamponade. LA = left atrium; LV = left ventricle; RV = right ventricle.
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6.19 U-SEE abdominal ultrasonogram showing hepatomegaly and congested hepatic veins in a dog with right-sided congestive heart failure. The appearance of the distended hepatic veins is sometimes referred to as the ‘bunny sign’.
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6.20 U-SEE abdominal ultrasonogram of the distal aorta in a dog with paraplegia. A large thrombus is occluding the aorta. Colour flow Doppler shows the absence of blood flow through the aorta.
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6.21 Lead I, II and III ECG recording from an 8-year-old large-breed dog presented with weakness and dyspnoea. There is a fast, regular narrow QRS complex tachycardia (QRS width <70 ms) at 300 bpm. The dog had tachycardia-induced cardiomyopathy and was in left-sided congestive heart failure with pulmonary oedema at initial presentation. Paper speed 50 mm/s; gain 5 mm/mV.
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6.22 Lead I, II and III ECG recording from a 7-year-old Boxer with severe subaortic stenosis and congestive heart failure. There is an irregularly irregular narrow QRS complex tachycardia, no P waves and just baseline undulations (f waves). The dog was in atrial fibrillation with a rapid ventricular response rate of 190–270 bpm. Paper speed 50 mm/s; gain 5 mm/mV.
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6.23 Lead I, II and III ECG recording from a 6-year-old Boxer with ventricular tachycardia. Note the broad QRS tachycardia (QRS width >70 ms) and very fast rate (500 bpm). This is a life-threatening arrhythmia that requires immediate emergency intervention. Paper speed 50 mm/s; gain 5 mm/mV.
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6.24 Lead I, II and III ECG recording from a dog presented for exercise intolerance and syncope. There is complete atrioventricular dissociation with a ventricular escape rhythm at 55 bpm and an atrial rate of 200 bpm. This is diagnostic of a third-degree atrioventricular block. Paper speed 50 mm/s; gain 5 mm/mV.
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6.25 Lead I, II and III ECG recording from a West Highland White Terrier presented for collapse. There is a short run of a narrow QRS tachycardia (QRS width <70 ms) (between the second and tenth QRS complexes) at 200 bpm followed by a 1.8 second sinus arrest. The pause is interrupted by a ventricular escape complex and the supraventricular tachycardia restarts. This is an example of tachycardia–bradycardia syndrome or sick sinus syndrome. Paper speed 50 mm/s; gain 5 mm/mV.
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6.26 Lead II ECG recording from a cat presented after being hit by a car. There are no P waves or any other atrial activity (flat baseline), the T waves are large and ‘tented’. This is a sinoventricular rhythm at 60 bpm. The cat had a bladder rupture and was severely hyperkalaemic, which resulted in atrial standstill. Paper speed 25 mm/s; gain 10 mm/mV.
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6.27 How heart (‘pump’) failure manifests clinically. There is evidence of underlying heart disease but no evidence of forward or backward heart failure. There is evidence of pulmonary and/or systemic venous congestion, but cardiac output is maintained. There is evidence of decreased cardiac output, but not of pulmonary and/or systemic venous congestion. There is evidence of decreased cardiac output and pulmonary and/or systemic venous congestion.
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6.28 (a) Lateral and (b) ventrodorsal thoracic radiographs of a dog with advanced myxomatous mitral valve disease and left-sided congestive heart failure. There is evidence of severe left atrial enlargement and an interstitial alveolar pattern in the perihilar and dorsocaudal lung fields, consistent with cardiogenic pulmonary oedema.
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6.29 (a) Lateral and (b) ventrodorsal thoracic radiographs of a dog with advanced dilated cardiomyopathy and left-sided congestive heart failure. There is evidence of left-sided cardiomegaly and an interstitial alveolar pattern in the perihilar and dorsocaudal lung fields, consistent with cardiogenic pulmonary oedema.
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6.30 (a) Lateral and (b) ventrodorsal thoracic radiographs of a cat with advanced cardiomyopathy and left-sided congestive heart failure. There is evidence of cardiomegaly and a diffuse alveolar pulmonary pattern consistent with pulmonary oedema. In cats, cardiogenic pulmonary oedema often does not show a typical caudodorsal distribution pattern, as it does in dogs. The pulmonary pattern associated with pulmonary oedema in cats may have any type of distribution (i.e. focal, diffuse or multifocal interstitial to alveolar pattern).
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6.31 (a) Lateral and (b) dorsoventral thoracic radiographs of a cat with pleural effusion, which is obscuring the cardiac silhouette.
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6.33 (a) Haemangiosarcoma in the right atrium. (b) Chemodectoma encirling the aorta (heart base tumour). These are the two most commonly detected cardiac masses. Differentiation between the two types of neoplasm is important because they are associated with different prognoses. LA = left atrium; LV = left ventricle; RV = right ventricle.
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6.34 Lead I, II and III ECG recording from a 9-year-old German Shepherd Dog with severe pericardial effusion showing electrical alternans. Note the variation in height of QRS complexes with alternating beats. Paper speed 50 mm/s; gain 5 mm/mV. (Courtesy of Dr T Glaus)
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6.35 (a) Left lateral and (b) ventrodorsal thoracic radiographs from a dog with large-volume pericardial effusion. Note the severe cardiomegaly, rounded shape and sharp margins of the cardiac silhouette. On the lateral view the shape of the cardiac silhouette resembles a ‘football’.
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6.39 Lead II ECG recording from a dog with low-grade second-degree atrioventricular block. Note the single blocked P wave. Paper speed 25 mm/s; gain 10 mm/mV.
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6.40 Lead I, II and III ECG recording from a dog with high-grade (4:1) second-degree atrioventricular block. Paper speed 50 mm/s; gain 5 mm/mV.
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6.41 Lead I, II and III ECG recording from a dog with two single atrial premature complexes (the 3rd and 7th complexes). Paper speed 50 mm/s; gain 5 mm/mV.
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6.42 Lead II ECG recording from a dog. Every sinus complex is followed by a ventricular premature complex in a repeating pattern. This is called ventricular bigeminy. Paper speed 50 mm/s; gain 10 mm/mV.
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6.43 Lead II ECG recording from a dog. These close-coupled ventricular premature contractions show R-on-T phenomenon. Paper speed 25 mm/s; gain 10 mm/mV.
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6.44 Lead I, II and III ECG recording from a cat. There is a short paroxysm of ventricular tachycardia lasting for nine beats. Paper speed 25 mm/s; gain 20 mm/mV.
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6.45 Lead I, II and III ECG recording from a dog with a fast, regular, wide QRS complex tachycardia (QRS width >70 ms). The dog was in sustained ventricular tachycardia at a rate of 370 bpm. Paper speed 50 mm/s; gain 5 mm/mV.
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6.46 Lead I, II and III ECG recording from a dog with an accelerated idioventricular rhythm (AIVR). The AIVR competes with the underlying sinus rhythm as the rate of each rhythm is similar. Paper speed 50 mm/s; gain 5 mm/mV.
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6.47 Lead II ECG recording from a dog that had a cardiac arrest during anaesthesia. There are irregular baseline undulations with no discernible P, QRS or T waves. The dog was in ventricular fibrillation. Paper speed 25 mm/s, 10 mm/mV.
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6.48 (a) Cat with left forelimb monoplegia due to arterial thromboembolism. (b) There is marked cyanosis of the footpads of the affected limb. (Courtesy of Dr T Glaus)

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