Application of step-wise discriminant analysis and Bayesian classification procedure in determining prognosis of acute myocardial infarction

A retrospective study was carried out to assess the feasibility of computer-assisted prognostication by discriminant analysis and the Bayesian classification procedure based on clinical information collected on patients with acute myocardial infarction. The overall accuracy was 94.2% in predicting hospital death but the prediction of late death after discharge was less accurate. It was found that not all of the 44 variables used for analysis were necessary to reach the same level of predictive accuracy--16 to 20 variables would result in almost the identical prediction. The Bayesian classification procedure was applied to estimate probabilities of individual patients belonging to the different prognostic categories.

Echocardiographic measurement of cardiac output using the mitral valve and aortic root echo

The current echo method for measuring cardiac output (CO) has various technical limitations and is based on the assumptions that the left ventricle is not dilated and that it contracts uniformly. We have taken a different approach to measuring CO by echo: CO = cross-sectional area of aortic root X left ventricular ejection time X mean aortic flow velocity X heart rate. Using the Fick method, 34 measurements of CO were made in patients with normal aortic and mitral valves, with simultaneous echo recordings from the aortic and mitral valves. The systolic closure slope of the anterior mitral valve leaflet was assumed to represent the mean aortic flow velocity. CO by Fick and the proposed echo method correlated well, both in patients with (r = 0.94) and those without (r = 0.87) asynergy and the overall correlation was strong (r = 0.90). Using the conventional echo and Fick methods, a much weaker association was found between the two measurements in those patients with asynergy (r = 0.44) as opposed to those without asynergy (r = 0.77).

Abolition of ischemic response to atrial pacing following aortocoronary bypass surgery

To determine the effect of successful aortocoronary bypass surgery (ACBS) on left ventricular (LV) function, the ischemic response to right atrial pacing (RAP) was studied in 22 angina patients before and 3.8 +/- 1.1 months after surgery. All patients were free of angina after ACBS and had at least one patent graft. Before ACBS, RAP induced angina in 15 patients (Group 1) but not in 7 patients (Group 2). After ACBS, no patient had angina with RAP despite the increased maximum rate of pacing. Post-pacing LV end-diastolic pressure (LVEDP) after ACBS decreased in Group 1 from 25 +/- 6 to 15 +/- 6 mm Hg (P less than 0.01), but not in Group 2. Changes in ejection fraction, cardiac output, resting LVEDP, or LVEDP after LV angiography were not significant in either group and were therefore not useful in evaluating the result of ACBS. However the ischemic response to right atrial pacing was abolished by successful aortocoronary bypass surgery, suggesting improved myocardial perfusion during stress.

False left ventricular aneurysm as a complication of open heart surgery

A false aneurysm developed at the site of left ventricular venting in an 8-year-old boy who had undergone aortic valve commissurotomy under cardiopulmonary bypass. The diagnosis was made by clinical examination and chest radiography and confirmed by left ventricular cineangiography. The aneurysm was successfully resected.

Long-term survival after isolated replacement of mitral valve with ball-valve prosthesis

In 111 patients whose diseases mitral valve was replaced with a ball-valve prosthesis the actuarial survival rate, including the hospital mortality of 10.8%, was 66% after 5 years and 59% after 8 years of follow-up. This suggests that in patients with moderate or severe symptoms due to mitral valve disease, replacing the valve can prolong life. However, in patients with no cardiac symptoms or with sinus rhythm and mild symptoms, it is doubtful that mitral valve replacement can prolong life, for the prognosis in these patients is favourable without operation.

Clinical echocardiography - an overview

Echocardiography is a new diagnostic technique for noninvasive assessment of the size, structure and function of the heart, using pulsed ultrasound. The physical principles underlying the generation of the ultrasonic signal for diagnostic use and the three modes (A, B and M) of displaying the reflected "echo" signal are briefly discussed. A full echographic study of the heart includes evaluation of the dimensions and patterns of movement of its various structures and chambers. The normal anatomic relations and echographic appearances of these structures and the changes they undergo in some of the more commonly recognized clinical conditions are described. Assessment of output and contractile behaviour of the left ventricle and recognition of various congenital heart defects are two of the more recent applications of this technique. Two-dimensional sector and multiscanning devices permit several areas of the heart to be visualized simultaneously in "real time".

Long-term survival after aortic valve replacement using Smeloff-Cutter prosthesis

The long-term prognosis of 187 consecutive patients who received single aortic valve replacement using Smeloff-Cutter prosthesis was studied. Of the 163 patients who survived the operation, a long-term follow-up (up to eight years) was obtained in 153 patients (95%). A total of 34 patients (22%) died during the follow-up period. Including the hospital mortality, the actuarial survival rate of our patients with Smeloff-Cutter prosthesis was 0.69 after the fifth year and 0.611 after the eighth year of follow-up. This is similar to the actuarial survival rate of patients with Starr-Edwards prosthesis but it appears significantly better than the expected survival rate of symptomatic patients with aortic stenosis treated without surgery. Thus, this result supports the contention that aortic valve surgery in properly selected patients can prolong life expectancy in addition to relieving symptoms in patients with aortic valve disease. The majority of surviving patients reported to have improved (88%) since the operation and to be symptom free (82%).

Ruptured aneurysms of sinuses of Valsalva

At least one additional cardiac lesion was present in 18 consecutive patients with ruptured aneurysms of the sinuses of Valsalva who were investigated between 1956 and 1973 at the University of Alberta Hospital. Clinical diagnosis was made in 78% (14/18) of the patients. Confirmation at cardiac catheterization, operation or autopsy was obtained in all but one. The main sites of rupture were the right ventricle (seven cases), right atrium (five) and left ventricle (five). Fifty percent (9/18) are alive and well following prompt operative repair, an average of 8.2 years later (range, six months to 15 years). Replacement of the aortic valve was associated with a high mortality (50% early, 13% late, total 63%) which could be explained by the higher operative risk in this group of very ill patients. Eight patients (44.4%) had had bacterial endocarditis prior to presentation and this may have played a significant role in the rupture of the sinus of Valsalva aneurysm.