Related Experiment Videos
Left ventricular mechanical efficiency in coronary artery disease
Insights
Prior myocardial infarction significantly reduces cardiac efficiency in patients with coronary artery disease by decreasing left ventricular work, despite normal oxygen consumption. This impaired efficiency correlates with reduced ejection phase indexes, highlighting a key impact on heart function.
Area of Science:
- Cardiology
- Cardiac Energetics
- Myocardial Infarction
Background:
- Coronary artery disease (CAD) and myocardial infarction (MI) can profoundly affect cardiac function.
- Understanding the impact of these conditions on cardiac energetics is crucial for patient management.
Purpose of the Study:
- To determine the effect of CAD and prior MI on cardiac energetics.
- To measure left ventricular myocardial blood flow, oxygen consumption (MVO2), efficiency, and ejection phase indexes in patients with and without prior MI.
Main Methods:
- Studied 36 patients undergoing coronary arteriography: 8 controls, 15 with CAD, and 13 with CAD and prior MI.
- Measured left ventricular myocardial blood flow (xenon-133 clearance), MVO2, and calculated efficiency from left ventricular work and oxygen content.
- Assessed left ventricular volumes, mass, and ejection phase indexes using quantitative left ventriculography.
Main Results:
- Left ventricular myocardial blood flow was reduced in CAD and prior MI groups compared to controls, but total flow was maintained due to increased mass.
- MVO2 did not differ significantly among the three groups.
- Patients with prior MI showed reduced left ventricular work and significantly decreased efficiency (15.9% vs. 28.8% in controls).
- Reduced efficiency correlated with impaired ejection fraction and myocardial shortening indexes.
Conclusions:
- In patients with prior MI, cardiac efficiency is significantly reduced due to diminished left ventricular work and normal MVO2.
- Reduced efficiency post-MI correlates with impaired ejection phase indexes, indicating a functional deficit.
- CAD patients without prior MI maintained normal MVO2 and efficiency.
Abstract:
The effect of coronary artery disease and prior myocardial infarction on cardiac energetics was determined by measuring left ventricular myocardial blood flow, oxygen consumption (MVO2), efficiency and ejection phase indexes in 36 patients undergoing coronary arteriography. Eight control patients with normal coronary arteriograms and normal left ventricular function, 15 patients with coronary artery disease without prior myocardial infarction and 13 patients with coronary disease and prior myocardial infarction (greater than 6 months) were studied. Left ventricular efficiency was calculated from left ventricular work, myocardial blood flow (measured by clearance of intracoronary xenon-133), and aortic and coronary sinus oxygen content. Left ventricular volumes, mass and ejection phase indexes were measured by quantitative left ventriculography. Left ventricular myocardial blood flow per 100 g/min was reduced in patients with coronary artery disease (49.0 +/- 8; p less than 0.01) and in patients with myocardial infarction (51.6 +/- 10; p less than 0.05) compared with control subjects (62.4 +/- 16), but total left ventricular flow was not reduced because of increased left ventricular mass. As a result, MVO2 did not differ significantly for the three patient groups (control 13.3, coronary artery disease 14.0 and myocardial infarction 14.3 ml/min). In the patients with myocardial infarction, left ventricular work index was reduced (2.4 versus 4.0 kg X m/m2 per min in the control group; p less than 0.001), causing efficiency to be reduced (15.9 versus 28.8% in the control group; p less than 0.001). Decreased efficiency correlated with ejection fraction (r = 0.54), mean velocity of circumferential fiber shortening (MVcf) (r = 0.45) and mean percent chordal shortening (r = 0.43) (all p less than 0.01). These data indicate that in control patients with normal coronary arteriograms, left ventricular myocardial efficiency averages 29%; in patients with coronary disease without myocardial infarction, left ventricular MVO2 and efficiency are in the normal range; in patients with prior myocardial infarction, left ventricular efficiency is significantly reduced as a result of diminished left ventricular work and normal MVO2; and reduced efficiency after myocardial infarction correlates with reduced ejection phase indexes.