Objectives: This study was performed to examine the prevalence of postembolic spectral patterns in patients with prosthetic heart valves and evaluate their potential relation to the underlying embolic material. Methods: The prevalence of the tail (TS) and lambda (LS) signs was examined in artifact signals and microembolic signals (MES) detected in 10 patients with prosthetic heart valves and 13 further patients with artificial heart valves during normobaria as well as during hyperbaric exposure (2.5 and 1.75 bar). Results: A total of 1,721 MES were detected in the 10 patients; prevalence of TS and LS were 11 and 9.8%, respectively. Hyperbaric exposure in the second group of patients resulted in a significant increase of the prevalence of LS (13.7% at 2.5 bar and 9.2% at 1.75 bar, as compared to 7.7 and 8.2% during normobaria), while the prevalence of TS remained unchanged, ranging between 5 and 6.7%. Neither TS nor LS was observed following artifact signals. Conclusions: TS and LS showed a high specificity (100%) but low sensitivity (ranging between 7.7 and 11 and 5 and 9.8%, respectively) for the detection of MES. LS appear to be – at least partially – associated with gaseous embolic material.

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Furui E, Hanzawa K, Ohzeki H, Nakajima T, Fukuhara N, Takamori M: ‘Tail sign’ associated with microembolic signals. Stroke 1999;30:863–866.
Baumgartner RW, Frick A, Kremer C, Oechslin P, Russi E, Turina J, Georgiadis D: Transcranial Doppler monitoring of patients with prosthetic heart valves during hyperbaric exposure. J Thorac Cardiovasc Surg 2001;122:1142–1146.
Georgiadis D, Wenzel A, Lindner A, Zerkowski HR, Zierz S: Automated intraoperative detection of Doppler microembolic signals using the bigate approach. Stroke 1998;29:137–140.
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