Rare case of paradoxical embolism causing myocardial infarction: successfully aborted by aspiration alone.

A 58-year-old male presented with severe substernal chest pain along with bilateral lower extremity pain. He was tachycardic, tachypneic, and hypoxic with tender right calf. Electrocardiogram showed ST elevation in anterior-lateral leads. Emergency coronary angiography revealed widely patent proximal left anterior descending (LAD) artery and total distal occlusion with an abrupt cut-off. The remaining coronary arteries did not have significant disease. An Export aspiration catheter was used and thrombus was aspirated from the LAD with return of TIMI flow grade 3 and normalization of the ST elevations. Doppler ultrasound revealed deep vein thrombosis; transthoracic echocardiogram using agitated saline echocontrast showed a patent foramen ovale. Nearly 5% of patients with ST elevation myocardial infarction do not have demonstrable atherosclerosis by coronary angiography; paradoxical coronary embolism is among the leading causes in such cases. Paradoxical embolism to the coronary tree is under diagnosed and its antemortem diagnosis is difficult. Information regarding appropriate management of myocardial infarction due to coronary embolism is scant. Aspiration of intracoronary thrombus provides good clinical results, avoiding clot fragmentation and balloon injury associated with angioplasty. We present a rare case of antemortem diagnosis of paradoxical embolism to the coronary artery successfully treated with aspiration alone.

Myocardial performance index correlates with right ventricular ejection fraction measured by nuclear ventriculography.

BACKGROUND: Assessment of right ventricular (RV) ejection fraction (EF) by two-dimensional echocardiography (2D ECHO) is practical but limited because of complex geometry of the RV. Techniques used for accurate measurement of RV EF are invasive or costly. However, derivation of 2D ECHO Doppler parameters to estimate RV function could be useful and inexpensive. METHODS: RV EF measured by nuclear ventriculography was compared with 2D ECHO estimates of myocardial performance index (MPI) and peak tricuspid annular systolic velocity (PTASV). Linear regression analysis and sensitivity analysis were used to analyze the data. RESULTS: RV EF measured by nuclear ventriculography correlated with MPI significantly (r =-0.55, P = 0.005) but not with PTASV (r = 0.09, P = 0.69). Using abnormal RV EF <45% measured by nuclear ventriculography, the sensitivity and specificity for MPI > 0.50 were 45.4% and 100%, respectively. The sensitivity and specificity of PTASV < or = 17.25 cm/sec in detecting abnormal RV EF were 100% and 35.4%. CONCLUSION: MPI greater than 0.50 indicates that RV function is abnormal and a value of PTASV > 17.25 cm/sec indicates normal RV function.

Chromosomal DNA transfer in Mycobacterium smegmatis is mechanistically different from classical Hfr chromosomal DNA transfer.

Classical conjugal DNA transfer of chromosomal DNA in bacteria requires the presence of a cis-acting site, oriT, in the chromosome. Acquisition of an oriT occurs if a conjugative plasmid integrates into the chromosome to form an Hfr donor strain, which can transfer extensive regions of chromosomal DNA. Because oriT sequences are unique, and because transfer occurs in a 5' to 3' direction, the frequency with which a particular gene is inherited by the recipient depends on the gene's location: those closest to the 3' side of oriT are transferred most efficiently. In addition, as the entire chromosome must be transferred to regenerate oriT, Hfr transconjugants never become donors. Here we describe novel aspects of a chromosomal DNA transfer system in Mycobacterium smegmatis. We demonstrate that there are multiple transfer initiations from a donor chromosome and, as a result, the inheritance of any gene is location-independent. Transfer is not contiguous; instead, multiple non-linked segments of DNA can be inherited in a recipient. However, we show that, with appropriate selection, segments of DNA at least 266 kb in length can be transferred. In further contrast to Hfr transfer, transconjugants can become donors, suggesting that the recipient chromosome contains multiple cis-acting sequences required for transfer, but lacks the trans-acting transfer functions. We exploit these observations to map a donor-determining locus in the M. smegmatis chromosome using genetic linkage analysis. Together, these studies further underline the unique nature of the M. smegmatis chromosomal transfer system.

The RD1 virulence locus of Mycobacterium tuberculosis regulates DNA transfer in Mycobacterium smegmatis.

Conjugal DNA transfer occurs by an atypical mechanism in Mycobacterium smegmatis. The transfer system is chromosomally encoded and requires recipient recombination functions for both chromosome and plasmid transfer. Cis-acting sequences have been identified that confer mobility on nontransferable plasmids, but these are larger and have different properties to canonical oriT sites found in bacterial plasmids. To identify trans-acting factors required for mediating DNA transfer, a library of transposon insertion mutants was generated in the donor strain, and individual mutants were screened for their effect on transfer. From this screen, a collection of insertion mutants was isolated that increased conjugation frequencies relative to wild type. Remarkably, the mutations map to a 25-kb region of the M. smegmatis chromosome that is syntenous with the RD1 region of Mycobacterium tuberculosis, which is considered to be the primary attenuating deletion in the related vaccine strain Mycobacterium bovis bacillus Calmette-Guérin. The genes of the RD1 region encode a secretory apparatus responsible for exporting Cfp10- and Esat-6, both potent antigens and virulence factors. In crosses using two M. smegmatis donors, we show that wild-type cells can suppress the elevated transfer phenotype of mutant donors, which is consistent with the secretion of a factor that suppresses conjugation. Most importantly, the RD1 region of M. tuberculosis complements the conjugation phenotype of the RD1 mutants in M. smegmatis. Our results indicate that the M. tuberculosis and M. smegmatis RD1 regions are functionally equivalent and provide a unique perspective on the role of this critical secretion apparatus.