The role of physician performed transthoracic echocardiography in emergency medicine

© 2013 Dr. Darsim Lattif HajiThere is increased realization of the emerging role of point of care transthoracic echocardiography as “ultrasound assisted examination”, given the low sensitivity of clinical examination for cardiovascular pathologies and the time critical nature of these pathologies. There is evidence that point of care transthoracic echocardiography provides higher accuracy in patient assessment and management, with potential prognostic impact by assessing the severity of cardiac dysfunction and response to treatment. Point of care transthoracic echocardiography is increasingly used by non cardiologists, as a diagnostic, screening or monitoring tool. The literature shows that TTE identifies new clinical findings; and conversely can accurately rule out clinically important pathologies. The diagnostic capability of new portable devices is improving rapidly and outdating its predecessors, thereby improving confidence in echocardiography findings. Parallel to this advancement in technology, there has also been an increase demand for training and curricula development in critical care echocardiography. This PhD thesis consists of a review of literature addressing the diagnostic and management impact of clinicians performed TTE in emergency medicine, intensive care and anaesthesia, accuracy of TTE in cardiac function assessment when performed by the treating clinicians. The review is followed by an educational study (chapter three) in critical care TTE training and a validation study in chapter four assessing Doppler parameters and interatrial septal movement during five perioperative periods in coronary artery bypass surgery using both transthoracic and transoesophageal echocardiography. The second half of the thesis describes the role of echocardiography in emergency department patients. Four cohorts of patients of non traumatic hypotension, shortness of breath, chest pain and fractured neck of femur were prospectively evaluated. In the educational study, the interpretative skills of one hundred participants, who completed an education program in limited transthoracic echocardiography, were assessed. Medical practitioners who completed the structured educational program showed good agreement with experts in interpretation of valve and ventricular function. A high level of agreement was observed in ventricular volume assessment (left 95%, right 96%), systolic function (left 99%, right 96%), left atrial pressure (96%) and haemodynamic state (97%). The highest failure to report answers (that is, no answer given) was for right ventricular volume and function. For moderate or severe valve lesions, agreement ranged from 90-98%, with failure to report < 5% in all cases except for mitral stenosis (18%). For mild valve lesions, the range of agreement was lower (53-100%) due to overestimation of severity. In the cardiac theatre study, 27 adult patients undergoing on-pump coronary artery surgery were included. Simultaneous echocardiographic and hemodynamic measurements were obtained immediately prior to anesthesia (TTE), after anesthesia and mechanical ventilation (TTE) and transoesophageal echocardiography, during conduit harvest (TOE), and after separation from cardiopulmonary bypass (TOE). In patients with low EF, Doppler parameters correlated well with pulmonary capillary wedge pressure measurements prior to anesthesia. However, after induction of anesthesia using either TTE or TOE, correlations were poor. In patients with normal ejection fraction, correlations were poor for both TOE and TTE at all stages of surgery. The sensitivity and specificity of echocardiographic values were not high enough to accurately predict raised pulmonary capillary wedge pressure except for a fixed curve pattern of interatrial septum (AUC 0.76 for PCWP ≥ 16, 0.89 for ≥ 17, and 0.98 for ≥ 18 mmHg) and S/D < 1, (AUC 0.74 for PCWP ≥ 16, 0.74 for ≥ 17, and 0.78 for ≥ 18 mmHg). In the four Emergency Department prospective observational studies, a total of 286 emergency department patients underwent an emergency physician-performed focused TTE after standard clinical assessment and initiation of treatment. The highest impact of TTE found was in 78 emergency department patients with non traumatic hypotension. Treatment changed in 50%. In this cohort, TTE impacted on differential diagnosis of 37.2% of patients. The impact on investigations, referral and disposition plans were 10.3%, 22% and 5.1%, respectively. Mortality was associated with TTE findings of right ventricular failure (35% vs. 8% p= 0.003), moderate to severe aortic valve stenosis (30% vs. 11%, p=0.04) and moderate to severe tricuspid valve regurgitation (48% vs. 17%, p=0.003). In the shortness of breath group, TTE helped to change the primary diagnosis in 37.6% of patients. The primary diagnosis changed to cardiac from non cardiac in 21% and from cardiac to non cardiac in another 9% of 85 patients. A high impact on treatment (40%) was also observed. The changes in primary diagnosis lead to 35% in referral. However the impact on investigations, and disposition plans were less, 10.4% and 17%, respectively. The impact on emergency department patients with chest pain was less with 22.8% change in diagnosis and only 7.6% change in investigations. Similarly a lower than hypothesized change in management was observed with 17.7% change in treatment, 12.7% change in referral and 21.8% change in disposition. The impact of TTE on cause of fall in the fractured neck of femur cohort was 13%, but 40.9% change in treatment was observed primarily due to the identification of an empty haemodynamic state in the group. A lower impact of 11.4% change in referrals and 4.5% change in disposition was observed