De-mystifying the certification process.
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Certification↗
Biomedical subjects
J E Gage
Publications and source records attributed to J E Gage.
Coronary vasomotor tone during static and dynamic exercise.
Coronary vasomotion is an important determinant of myocardial perfusion in patients with angina pectoris, and it influences not only normal but also stenotic coronary arteries. The ability of a stenotic coronary artery to change its size is dependent on the presence of a normal musculo-elastic wall segment within the stenosis (i.e., eccentric stenosis). Coronary vasoconstriction of normal and stenotic coronary arteries has been reported by Brown and coworkers (Circulation 1984; 70: 18-24) during isometric exercise. The effect of dynamic exercise on coronary vasomotion was evaluated in one group of 13 patients with ischaemia-like symptoms and normal coronary arteries (group 1) and in a second group of 12 patients with coronary artery disease with exercise-induced angina pectoris (group 2). Luminal area of a normal and a stenotic vessel segment was determined by biplane quantitative coronary arteriography at rest, during supine bicycle exercise and 5 min after administration of 1.6 mg sublingual nitroglycerin. Coronary sinus blood flow was measured in group 1 at rest and after 0.5 mg kg-1 intravenous dipyridamole using coronary sinus thermodilution. Coronary flow reserve was calculated from coronary sinus flow after dipyridamole divided by coronary sinus flow at rest. In group 1, coronary vasodilation of the large (i.e., proximal) and the small (i.e., distal) coronary arteries was observed during exercise in seven patients (subgroup A). However, in the remaining six patients (subgroup B) coronary vasoconstriction of the small arteries (-24%, P less than 0.001) was found during exercise, whereas the large vessels showed coronary vasodilation (+26%, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
Angina Pectoris↗
Diltiazem alone and combined with nitroglycerin: effect on normal and diseased human coronary arteries.
The vasodilatory effect of diltiazem and nitroglycerin on the large epicardial coronary arteries was evaluated in 26 patients with coronary artery disease. The luminal area of a normal and a stenotic coronary artery was determined at rest, after intracoronary administration of diltiazem, during submaximal exercise as well as 5 min after 1.6 mg sublingual nitroglycerin using biplane quantitative coronary arteriography. Twelve patients with no pretreatment prior to the exercise test served as group 1 (controls) and 14 patients with intracoronary administration of 2 to 3 mg diltiazem prior to the exercise test as group 2. Normal vessel: In the control group luminal area increased significantly during exercise (+23%, P less than 0.01) and after sublingual administration of nitroglycerin (+40%, P less than 0.001). In group 2 luminal area increased after intracoronary administration of diltiazem (+19%, P less than 0.01), during bicycle exercise (+23%, P less than 0.001) and after sublingual administration of nitroglycerin (+39%, P less than 0.001). Stenotic vessel: In the control group luminal area decreased significantly (-29%, P less than 0.001) during bicycle exercise but increased after sublingual administration of nitroglycerin at the end of the exercise test (+12%, NS vs. rest). In group 2 intracoronary administration of diltiazem was associated with a mild increase in stenosis area (+11%, P less than 0.05). There was a further increase in stenosis area during bicycle exercise (+23%, P less than 0.001 vs. rest) and after sublingual nitroglycerin (+32%, P less than 0.001). Coronary vasodilation of the stenotic segment was, however, significantly more pronounced after sublingual nitroglycerin in group 2 than 1 (+32% versus 12%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Vasoconstriction of stenotic coronary arteries during dynamic exercise in patients with classic angina pectoris: reversibility by nitroglycerin.
To study the vasomotility of normal and diseased coronary arteries during dynamic exercise, symptom-limited supine bicycle exercise during cardiac catheterization was performed by 18 patients with classic angina pectoris. The cardiovascular response was assessed by hemodynamic measurements and computer-assisted determination of normal and stenotic coronary artery luminal areas from biplane coronary angiograms made before, during, and after exercise. After baseline measurements were recorded, 12 patients (group 1) performed bicycle exercise for 3.4 min (mean), reaching a maximum workload of 81 W (mean); at the end of exercise they received 1.6 mg sublingual nitroglycerin. After measurements at rest in six other patients (group 2), 0.1 mg intracoronary nitroglycerin was given, followed by exercise (3.8 min, 96 W; NS) and sublingual nitroglycerin as in group 1. During exercise in group 1, luminal area of the coronary stenosis decreased to 71% of resting levels (p less than .001), while area of the normal coronary artery increased to 123% of control (p less than .001). After sublingual nitroglycerin at the end of exercise, area of the normal vessel further increased to 140% of control (p less than .001), while luminal area of the stenosis dilated to 112% of resting levels (p less than .001 vs exercise, NS vs rest). Pretreatment with intracoronary nitroglycerin increased both normal (121%; p less than .05) and stenotic (122%; p less than .05) luminal areas, while preventing the previously observed narrowing of stenosis during exercise (114%; NS). Exercise resulted in a similar heart rate-systolic pressure product and caused angina pectoris in two-thirds of the patients in each group. However, patients pretreated with intracoronary nitroglycerin (group 2) had a lower mean pulmonary arterial pressure during maximum exercise (35 mm Hg) than those patients (group 1) not receiving pretreatment (47 mm Hg; p less than .001). Group 2 patients reached a percentage of their predicted work capacity (65%) that was about the same as that during previous upright bicycle exercise (71%; NS), while group 1 patients had a significantly lower work capacity (51% of predicted) than that before catheterization (82%; p less than .001). Hence, narrowing of coronary artery stenosis during dynamic exercise is attributable to active vasoconstriction due to its reversibility by preexercise intracoronary nitroglycerin. Patients who did not experience narrowing of stenosis during exercise (group 2) had less evidence of myocardial ischemia (lower mean pulmonary arterial pressure) and maintained their work capacity.(ABSTRACT TRUNCATED AT 400 WORDS)
Adult↗
Diastolic filling dynamics in patients with aortic stenosis.
Left ventricular filling dynamics were investigated in 24 patients with aortic stenosis (AS). Biplane cineangiography was performed with simultaneous micromanometry in these 24 patients and in six control subjects. Twelve of the patients with AS had moderate hypertrophy with a left ventricular muscle mass index of less than 180 g/m2 (ASI group) and 12 had severe hypertrophy with an index of 180 g/m2 or more (AS2 group). Filling dynamics were also evaluated postoperatively in eight patients in the AS1 and six patients in the AS2 group. Preoperatively, end-diastolic and end-systolic volume indexes were larger and ejection fraction was lower in the AS2 compared with the control or AS1 group. Percent volume increase during the first half of diastole (%V1) was smaller in the AS1 than in the AS2 group. Peak filling rate in the first half of diastole (PFR 1) was higher in the AS2 than in the control or in AS1 group, while peak filling rate in the second half of diastole (PFR2) was considerably greater in the AS1 group than in the other two groups. The time constant of left ventricular pressure decline, an index of the rate of relaxation, was prolonged in the AS2 group. In contrast, mitral valve opening pressure (MVOP) was significantly higher in this group than in the other two groups. The constant of left ventricular chamber stiffness was slightly but not significantly greater in both AS groups than in the control subjects. After surgery in patients in the AS1 group, preoperatively reduced %V1 had increased and preoperatively enhanced PFR2 had decreased. In patients in the AS2 group, excluding one with a persistent low ejection fraction after surgery, preoperatively enhanced PFR1 decreased in association with a decrease in MVOP. Thus, left ventricular filling dynamics vary in patients with AS depending on the degree of left ventricular hypertrophy and systolic function. In patients with AS and moderate hypertrophy %V1 is slightly reduced but is compensated for by a forceful atrial contraction. In those with severe hypertrophy and systolic dysfunction increased driving pressure allows %V1 to remain within normal limits, despite prolonged left ventricular relaxation and decreased elastic recoil. Both changes in left ventricular filling dynamics tend to normalize after surgery in association with a reduction in left ventricular hypertrophy and/or an improvement of systolic function.
Adult↗
Suctioning of upper airway meconium in newborn infants.
To compare the efficacy of bulb and catheter suctioning of upper airway meconium in neonates, meconium labeled with technetium Tc 99m sulfur colloid was injected into the trachea and oropharynx of anesthetized kittens. Human birth conditions were simulated by an inflated blood pressure cuff around the thorax and abdomen of the animals and by partial degassing of the lungs before introduction of meconium. Distribution of meconium in the upper airway was determined by scintigraph. Catheter suction brought about a 43% decrease in radioactivity while there was only a 1% decrease after bulb suctioning. Meconium may persist in the trachea for more than 20 minutes after introduction, indicating the desirability of continued suctioning efforts in neonates with meconium aspiration syndrome. The relative safety of the two techniques was not assessed.
Airway Obstruction↗
Cause of electromechanical dissociation.
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Blood Volume↗
Complement activation in patients undergoing mechanical circulatory support.
Contact of blood with artificial surfaces activates pro-inflammatory responses and the complement cascade. This may have broad implications on the post implantation fate of patients needing mechanical circulatory support. Therefore, we investigated the course and prognostic value of complement factors C3a and C5a in 66 patients supported with pulsatile ventricular assist devices. All patients were in severe cardiogenic shock, i.e., catecholamine dependent and in the intensive care unit, before implementation of mechanical circulatory support. Isolated left ventricular support (Novacor [Oakland, CA] or Thermo Cardiosystems, Inc. [TCI; Woburn, MA]) was used in 28 patients, and biventricular support (Berlin Heart [Mediport, Berlin, Germany]) in 38 patients. Before initiation of mechanical circulatory support, no statistically significant differences in C3a or C5a between surviving and nonsurviving patients with left ventricular assist devices (LVADs) were found. Patients with biventricular assist devices (BVADs) had significantly higher C3a (804 +/- 364 ng/L) levels than patients with LVADs (536 +/- 204 ng/L, p = 0.02) before mechanical circulatory support. Only C5a, only in the BVAD group, was able to predict patients' post implantation course before implantation of a ventricular assist device (p = 0.02). Three weeks after initiation of mechanical circulatory support, complement factors remained increased in all groups. There was no difference, however, in complement activation between patients with LVADs and those with BVADs. Patients not reaching transplantation had significantly higher C3a levels at this point than those successfully supported (p = 0.007). The degree of complement activation mainly depends on the severity of cardiogenic shock before initiation of mechanical circulatory support, and not on the device used. Patients with extremely high levels of complement activation before implantation of the device could be saved with BVAD rather than LVAD support. Patients who continued to have highly elevated complement levels 3 weeks after initiation of mechanical circulatory support had unfavorable prognoses. Complement activation indicates the severity of cardiogenic shock before implementation of mechanical circulatory support and the degree of recovery from secondary organ dysfunction while on the device. It is fairly independent of the system used for mechanical circulatory support, and therefore can be applied to predict patients' post implantation course and outcome.
Adolescent↗