Citations

SUMMARY Real-time PCR has revolutionized the way clinical microbiology laboratories diagnose many human microbial infections. This testing method combines PCR chemistry with fluorescent probe detection of amplified product in the same reaction vessel. In general, both PCR and amplified product detection are completed in an hour or less, which is considerably faster than conventional PCR detection methods. Real-time PCR assays provide sensitivity and specificity equivalent to that of conventional PCR combined with Southern blot analysis, and since amplification and detection steps are performed in the same closed vessel, the risk of releasing amplified nucleic acids into the environment is negligible. The combination of excellent sensitivity and specificity, low contamination risk, and speed has made real-time PCR technology an appealing alternative to culture- or immunoassay-based testing methods for diagnosing many infectious diseases. This review focuses on the application of real-time PCR in the clinical microbiology laboratory.

Background— The impact of aortic prosthesis-patient mismatch (P-PtM) on long-term survival is unclear. Methods and Results— Between 1985 and 2000, 388 patients at Mayo Clinic in Rochester, Minn, underwent aortic valve replacement (AVR) with 19- or 21-mm St Jude Medical prostheses and had transthoracic echocardiography within 1 year after AVR. Mean age of patients was 62±13 years; 69% were female. Prosthesis effective orifice area (EOA) was derived from the continuity equation. P-PtM was classified as severe (indexed EOA ≤0.60 cm 2 /m 2 ), moderate (0.60 cm 2 /m 2 <indexed EOA≤0.85 cm 2 /m 2 ), or not hemodynamically significant (indexed EOA >0.85 cm 2 /m 2 ). P-PtM was severe in 66 patients (17%), moderate in 168 (43%), and not hemodynamically significant in 154 (40%). Patients with severe P-PtM had a significantly larger body surface area ( P <0.0001), higher mean gradient ( P <0.0001), lower preoperative ( P <0.0001) and postoperative ( P <0.0001) ejection fractions, and lower stroke volume ( P <0.0001) and more often received a 19-mm prosthesis ( P =0.0008) than patients with moderate or no hemodynamically significant mismatch. For patients with severe mismatch, 5-year survival rates (72±6%) and 8-year survival rates (41±8%) were significantly less than for patients with moderate mismatch (80±3% and 65±5%; P =0.026) or no hemodynamically significant mismatch (85±3% and 74±5%; P =0.002). On multivariate analysis after adjustment for other predictors of outcome, severe mismatch was associated with higher mortality (hazard ratio 2.18; 95% confidence interval 1.24 to 3.85; P =0.007) and higher incidence of congestive heart failure (hazard ratio 3.1; 95% confidence interval 1.3 to 7.4; P =0.009) than no hemodynamically significant mismatch. Conclusions— Severe P-PtM is an independent predictor of higher long-term mortality and congestive heart failure in patients with small St Jude Medical aortic valve prostheses. For patients undergoing AVR who are at risk of severe mismatch, every effort should be made to use a larger prosthesis or to consider a prosthesis with a larger EOA.