A computer model for the prediction of left epicardial coronary blood flow in normal, stenotic and bypassed coronary arteries, by single or sequential grafting.

This article describes a computer model for calculating left epicardial coronary blood pressure and flow waveforms of a right dominant coronary circulation. Using the geometry of 16 vascular branches and employing the one-dimensional Navier-Stokes equations the model allows for the prediction of blood pressure and flow patterns in normal and stenosed vessels. This model was also used to predict the haemodynamic changes observed after insertion of two single saphenous vein bypass grafts, as compared with the corresponding changes after insertion of a sequential (snake-like) saphenous graft. In normal vessels during systole and diastole, the pressure and the flow waveforms obtained showed patterns that correlate very well with the findings observed by other investigators using intracoronary flowmeter or Doppler velocimeter techniques. In coronary artery disease (90% stenoses in LAD and diagonal branch 1), the authors' main contribution is the reconfirmation of a previously described finding of systolic flow rises in stenotic segments. This finding seems to be an important compensatory mechanism, in contrast to normal coronary vessels, which maintain a mainly diastolic flow pattern. The introduction of single or sequential bypass grafts leads to pressure and flow restoration after graft revascularization. Besides this finding, the general concept of a diastolic flow restoration post-stenotically, in the previously decreased and systolic augmented flow areas, is also observed. The two revascularization methods were also compared with regard to their specific advantages, disadvantages and indications and were also extensively compared with several in vivo studies.

Mitral valve replacement in a Jehovah's Witness with dextrocardia and situs solitus.

BACKGROUND AND AIMS OF THE STUDY: Dextrocardia with situs solitus and mitral valve insufficiency requiring surgical treatment is a rare presentation. Jehovah's Witnesses (JW), a specific religious group, deny any blood transfusion and for this reason the cardiac surgeon has to plan his operation well in advance, particularly in the case of adhesions from previous thoracic procedures. MATERIALS AND METHODS: A 50-year-old white female Jehovah's Witness with dextrocardia and situs solitus was referred for surgical treatment of massive mitral valve insufficiency of rheumatic etiology. Due to multiple adhesions from previous bilateral thoracotomies and the inverted position of the heart, cardiopulmonary bypass (CPB) was initiated with an aortic and a left common femoral vein cannulae. CPB was completed with an additional SVC cannula. The surgeon, having excellent exposure from the opposite side of the table, was able to perform a mitral valve replacement (MVR) with a 31 mm St. Jude Medical valve prosthesis, through a giant left atrium under moderate hypothermia and crystalloid cardioplegia. The operation was bloodless, with only two units of autotransfused blood being used with a postoperative hematocrit of 34%. RESULTS: The patient had an uneventful recovery and has been in NYHA class I for 24 months now. CONCLUSIONS: The case is presented for the safety of the approach, the excellent exposure from the left side in a dextrocardia case and the avoidance of blood transfusion in a Jehovah's patient.