"Hands-Free" continuous echocardiography during treadmill exercise using a novel ultrasound transducer.

BACKGROUND: Echocardiographic imaging using a handheld transducer in conjunction with treadmill exercise testing is commonly used for the diagnosis of coronary artery disease. Motion of the hand and the transducer during peak exercise preclude optimal imaging. To circumvent the limitations of handheld transducers, we developed a low profile transducer (CONTISON) which can be attached to the chest wall for continuous cardiac imaging. METHODS AND RESULTS: This feasibility study was performed in 10 normal male subjects (28 to 36 years). The ultrasound transducer was placed in the third or fourth intercostal space at the left sternal border to permit imaging of the left ventricle in its short axis. The transducer was interfaced with a commercially available ultrasound machine. The left ventricle was imaged at rest and while subjects exercised according to a standard Bruce protocol. All segments of the left ventricular short axis were seen at rest and peak exercise. Increased left ventricular wall thickening and wall motion were seen at peak exercise. There were no complications from the procedure. CONCLUSION: We demonstrated the feasibility of hands-free left ventricular imaging during treadmill exercise using the CONTISON transducer. Further evaluation of the technique to detect stress-induced wall motion abnormalities, as a means of diagnosing myocardial ischemia, appears warranted. (ECHOCARDIOGRAPHY 2010;27:563-566).

"Hands-Free" continuous transthoracic monitoring of pericardiocentesis using a novel ultrasound transducer.

BACKGROUND: Pericardiocentesis can be monitored with a hand-held transducer. The purpose of this study was to assess the feasibility of monitoring pericardiocentesis using a novel ultrasound transducer, which can be attached to the chest wall, developed in our laboratory (CONTISON). METHODS: We studied nine patients with large pericardial effusions. The 2.5-MHz transducer is spherical in its distal part and mounted in an external housing to permit steering in 360 degrees. The external housing is attached to the chest wall using an adhesive patch. The CONTISON transducer was placed at the cardiac apex and an apical four-chamber view obtained. Pericardiocentesis was performed from the subcostal position. The pericardial effusion was continuously imaged. Mitral inflow velocity signals were recorded before and after pericardiocentesis. When fluid was first obtained, 50 mL of fluid were discarded after which 5 mL of agitated saline was injected through the needle. RESULTS: In the first patient the pericardiocentesis needle was seen in the left ventricular cavity. Saline injection produced a contrast effect in the left ventricle. The needle was gradually withdrawn until contrast was seen in the pericardial sac. A total of 1100 mL was removed without further complications. The second patient had clear fluid followed by blood stained aspirate. The echocardiogram revealed gradual appearance of granular echoes within the pericardial sac, suggestive of intrapericardial clot that was subsequently surgically evacuated. In the remaining seven patients, agitated saline produced a contrast effect in the pericardial sac indicative of proper needle position. Mitral flow velocity paradoxus was noted in five patients, and it resolved after pericardiocentesis in four patients. No adjustment of the transducer was required. CONCLUSION: The CONTISON transducer permitted continuous monitoring of pericardiocentesis. This technique could potentially facilitate pericardiocentesis.

Continuous recording of pulmonary artery diastolic pressure and cardiac output using a novel ultrasound transducer.

BACKGROUND: The feasibility of hands-free transthoracic continuous determination of pulmonary artery (PA) diastolic pressure (PAD) and cardiac output (CO) by Doppler ultrasound has not been previously demonstrated. We developed a 2.5-MHz spherical transducer mounted in an external housing to permit steering in 360 degrees (Contison). The external housing was attached to the chest wall using an adhesive patch. METHODS AND RESULTS: Fifty patients in the coronary care department who had PA catheters had Doppler ultrasound studies. The 2.5-MHz spherical transducer was placed at the left sternal border to permit imaging of the pulmonic valve and was attached to a commercial ultrasound machine. The PA was imaged and its diameter measured. The pulmonary flow velocity signal was recorded and the time velocity integral obtained. The CO was calculated as: CO = time velocity integral of the PA systolic flow velocity signal x pi diameter(2) divided by 4 x heart rate. The pulmonary regurgitation signal was then recorded and the end-diastolic velocity of the regurgitant signal was measured. Right atrial pressure was assessed from the jugular venous pressure or from the size and pulsatility of the inferior vena cava. The PADP was calculated as: PADP = 4 end-diastolic velocity of the regurgitant signal(2) + right atrial pressure. The CO, PADP, and pulmonary wedge pressure were recorded from the PA catheter immediately after the ultrasound studies. Serial data were obtained every half hour or 1 hour up to a maximum of 5 hours. Adequate Doppler signals were obtained in 43 patients. RESULTS: There was a good correlation between the PADP by Doppler versus PA catheter (r = 0.90, standard error of the estimate = 3.3 mm Hg); PADP by Doppler versus PA wedge pressure (r = 0.88, standard error of the estimate = 3.7 mm Hg); and CO by Doppler versus PA catheter (r = 0.92, standard error of the estimate = 0.7 L/min). CONCLUSION: The 2.5-MHz spherical transducer permitted accurate assessment of CO and PAD. This transducer could be of potential value in monitoring patients in the intensive care setting.