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Tissue Doppler
Advances
Page 3
Cardiology Tissue Doppler Background Conventional echocardiography is used to screen for dilated cardiomyopathy (DCM), and the diagnosis is made on the basis of detection of reduced inotropism, dilatation of cardiac chambers, and increased sphericity. However, ultrasonographically detectable functional and morphologic changes are sometimes absent in the presence of DCM depending on the stage of the disease. Conventional echocardiography is not sensitive for the diagnosis of the preclinical phase of DCM in dogs. Tissue Doppler imaging (TDI) may provide a more sensitive method of diagnosis of DCM, but the accuracy of TDI for early detection of naturally occurring DCM in dogs in a clinical setting has not been reported. Objectives To report use of tissue Doppler imaging to confirm the diagnosis of DCM in a dog with equivocal echocardiographic findings. Case Report A 1-year-old, female Great Dane was referred for echocardiographic examination prior to anesthesia for surgical correction of prolapse of the right third eyelid gland. The dog had no history of respiratory or cardiovascular disease. Physical examination findings were within normal limits.
Advances
Page 4
An ultrasound machine equipped with a 2.5 to 3.5-MHz phased-array transducer, 2-dimensional and M-mode echocardiography, color-flow imaging, spectral Doppler examination, and TDI was used with continuous electrocardiographic monitoring to evaluate the patient and performed by the same trained observer. According to the proposed conventional ultrasound criteria for the diagnosis of canine DCM, the total score for this dog was 4 (3 points for the slight decrease in the index of sphericity and 1 for the rare ventricular premature beats). However, a total minimum score of 6 is required to confirm DCM. On the basis of the TDI data, it was concluded that the dog had a severe systolic and early diastolic myocardial alteration consistent with DCM. As a result, surgical repair of the prolapsed third eyelid was cancelled, and the owner was advised to return the dog within the next 4 to 6 months for reevaluation of both conventional and TDI echocardiographic parameters. The owner complied with the advice and returned the dog for re-evaluation 4 months later. Progressive exercise intolerance was noticed by the owner since the last examination. Physical examination findings included normal capillary filling time and the color of the mucous membranes, tachypnea, and paroxysmal tachycardia with a weak arterial pulse. Thoracic radiography revealed left-sided cardiomegaly without pulmonary edema. The heart rate on electrocardiogram was more than 220 beats/min with episodes of unifocal ventricular tachycardia. Conventional echocardiography confirmed a marked systolic and diastolic left ventricular dilatation associated with a left atrial dilatation. The index of sphericity had decreased dramatically, i.e., there was a marked rounding of the left ventricle. Using the criteria for diagnosis of DCM in dogs, the total score for the dog was 8, consistent with DCM. Author Conclusion Severe myocardial alterations may be detected via TDI in dogs with equivocal echocardiographic findings of DCM. Inclusions Two figures, 2 tables, 18 references. Editor Annotation Most practitioners are probably unaware
of TDI. This is a relatively recent feature on some high-end echocardiographic machines that allows measurement of the velocity of the myocardium during contraction or relaxation. Different parts of the myocardium move with different speeds during contraction or relaxation (e.g., the endocardium moves much faster than the epicardium), and achieve different maximum velocities. Using low-speed settings and filtering the signal, cardiologists are able to measure these velocities. The Doppler-derived information can then be analyzed off-line to detect changes from“normal” profiles. Variables such as myocardial velocity gradient (MVG) and mean myocardial velocity (MMV) can be determined. The authors used TDI to identify a subnormal MVG in a young great Dane. They have previously published on the use of TDI in diagnosing myocardial abnormalities in male dogs with Duchenne’s muscular dystrophy (which develop systolic myocardial failure) prior to any standard echocardiographic evidence of systolic myocardial failure. This exciting prospect — the ability to diagnose occult DCM by echocardiography — needs much more rigorous clinical investigation. Longitudinal studies in dogs with occult DCM are needed to determine the sensitivity and specificity of the method. Other disease states (cardiac and non-cardiac) will need to be examined. Additionally, TDI requires specialized equipment, expertise, and substantial offline analysis, so it is not a technique that will be routinely available for veterinary practitioners or to even many veterinary cardiologists in the near future. (MR) Chetboul V, Sampedrano CC, Testault I, et al. Use of tissue Doppler imaging to confirm the diagnosis of dilated cardiomyopathy in a dog with equivocal echocardiographic findings. J Am Vet Med Assoc 2004;225:1877-1880.
Page 3
Cardiology Tissue Doppler Background Conventional echocardiography is used to screen for dilated cardiomyopathy (DCM), and the diagnosis is made on the basis of detection of reduced inotropism, dilatation of cardiac chambers, and increased sphericity. However, ultrasonographically detectable functional and morphologic changes are sometimes absent in the presence of DCM depending on the stage of the disease. Conventional echocardiography is not sensitive for the diagnosis of the preclinical phase of DCM in dogs. Tissue Doppler imaging (TDI) may provide a more sensitive method of diagnosis of DCM, but the accuracy of TDI for early detection of naturally occurring DCM in dogs in a clinical setting has not been reported. Objectives To report use of tissue Doppler imaging to confirm the diagnosis of DCM in a dog with equivocal echocardiographic findings. Case Report A 1-year-old, female Great Dane was referred for echocardiographic examination prior to anesthesia for surgical correction of prolapse of the right third eyelid gland. The dog had no history of respiratory or cardiovascular disease. Physical examination findings were within normal limits.
Advances
Page 4
An ultrasound machine equipped with a 2.5 to 3.5-MHz phased-array transducer, 2-dimensional and M-mode echocardiography, color-flow imaging, spectral Doppler examination, and TDI was used with continuous electrocardiographic monitoring to evaluate the patient and performed by the same trained observer. According to the proposed conventional ultrasound criteria for the diagnosis of canine DCM, the total score for this dog was 4 (3 points for the slight decrease in the index of sphericity and 1 for the rare ventricular premature beats). However, a total minimum score of 6 is required to confirm DCM. On the basis of the TDI data, it was concluded that the dog had a severe systolic and early diastolic myocardial alteration consistent with DCM. As a result, surgical repair of the prolapsed third eyelid was cancelled, and the owner was advised to return the dog within the next 4 to 6 months for reevaluation of both conventional and TDI echocardiographic parameters. The owner complied with the advice and returned the dog for re-evaluation 4 months later. Progressive exercise intolerance was noticed by the owner since the last examination. Physical examination findings included normal capillary filling time and the color of the mucous membranes, tachypnea, and paroxysmal tachycardia with a weak arterial pulse. Thoracic radiography revealed left-sided cardiomegaly without pulmonary edema. The heart rate on electrocardiogram was more than 220 beats/min with episodes of unifocal ventricular tachycardia. Conventional echocardiography confirmed a marked systolic and diastolic left ventricular dilatation associated with a left atrial dilatation. The index of sphericity had decreased dramatically, i.e., there was a marked rounding of the left ventricle. Using the criteria for diagnosis of DCM in dogs, the total score for the dog was 8, consistent with DCM. Author Conclusion Severe myocardial alterations may be detected via TDI in dogs with equivocal echocardiographic findings of DCM. Inclusions Two figures, 2 tables, 18 references. Editor Annotation Most practitioners are probably unaware
of TDI. This is a relatively recent feature on some high-end echocardiographic machines that allows measurement of the velocity of the myocardium during contraction or relaxation. Different parts of the myocardium move with different speeds during contraction or relaxation (e.g., the endocardium moves much faster than the epicardium), and achieve different maximum velocities. Using low-speed settings and filtering the signal, cardiologists are able to measure these velocities. The Doppler-derived information can then be analyzed off-line to detect changes from“normal” profiles. Variables such as myocardial velocity gradient (MVG) and mean myocardial velocity (MMV) can be determined. The authors used TDI to identify a subnormal MVG in a young great Dane. They have previously published on the use of TDI in diagnosing myocardial abnormalities in male dogs with Duchenne’s muscular dystrophy (which develop systolic myocardial failure) prior to any standard echocardiographic evidence of systolic myocardial failure. This exciting prospect — the ability to diagnose occult DCM by echocardiography — needs much more rigorous clinical investigation. Longitudinal studies in dogs with occult DCM are needed to determine the sensitivity and specificity of the method. Other disease states (cardiac and non-cardiac) will need to be examined. Additionally, TDI requires specialized equipment, expertise, and substantial offline analysis, so it is not a technique that will be routinely available for veterinary practitioners or to even many veterinary cardiologists in the near future. (MR) Chetboul V, Sampedrano CC, Testault I, et al. Use of tissue Doppler imaging to confirm the diagnosis of dilated cardiomyopathy in a dog with equivocal echocardiographic findings. J Am Vet Med Assoc 2004;225:1877-1880.