Left Ventricular Pressure -Volume Relationships and Myocardial Oxygen Consumption in the Isolated Heart

Abstract

HYPOTHESIS that the physical work performed during ventricular systole is largely determined hy ventricular diastolic volume has had currency for the last 45 years. 1 " 4 The oxygen cost of the heart's contraction has likewise been related to diastolic volume, and also to stroke work, mean arterial blood pressure times the heart rate, the integral of systolic pressure in time, and ventricular wall tension. 2 -3 ' r>~9 Many have attempted to identify the factors that determine the oxygen needs of the heart. Their conclusions have not been without controversy. As early as 1915, it was noted that "an increase of [cardiac] output was more economically performed than a comparable increase of 'aortic pressure'." 10 In 1927 Starling and Visscher, 2 and Hemingway and Fee, 5 indicated that myocardial oxygen consumption was dependent on diastolic volume even when distention of the ventricle had progressed to the point of diminished stroke work. Later studies relating myocardial oxygen consumption to the area under the systolic pressure tracing were interpreted to show that at a constant heart rate systolic pressure was the preponderant, if not the sole, determinant of myocardial oxygen consumption, and strongly implied that the metabolic needs of the heart were not determined by diastolic volume or diastolic fiber length. 7 ' 8 Eecent work in which left ventricular circumference was measured is consistent with this concept. 11 In these studies stroke volumes were known, but absolute volumes were not measured. The experiments described in this paper were dpsigned to control absolute ventricular volume accurately.The intact left ventricle of the dog has a fairly discrete blood supply and lends itself to metabolic determinations. 12 By means of a previously described preparation, 13 a combined pressure-volume and metabolic study was performed on an isovolumetrically contracting left ventricle. The preparation was also arranged to allow volume changes during systole and to permit the measurement of absolute volume. The isovolumetric pressurevolume studies, studies involving changes, and the results of concomitant metabolic determinations are reported in this paper. The intent was to relate myocardial oxygen consumption to ventricular pressure and volume, and to test specifically whether or not myocardial oxygen consumption is determined by diastolic volume. Methods Isovolumetric StudiesThe isolated heart preparation has been described previously in full 13 and will be described briefly herein. A schematic diagram of the preparation used for isovolumetric studies is seen in figure 1.Hearts from healthy mongrel dogs were rapidly excised under ehloralose-urethane anesthesia. A lucite button was ligated in the vicinity of the aortic cusps with a suture passed under the left coronary artery. By this procedure the left ventricular cavity was completely isolated from the coronary circulation. The right coronary artery was ligated, as were the bundle of His and the inferior and superior venae eavae. A catheter was placed in the coro...

Contractile state of the left ventricle in man as evaluated from end-systolic pressure-volume relations.

“…To validate this assumption, at least three data points (and therefore at least three ventricular angiographic studies using the methodology described above) would be required for each subject. However, in support of the assumption of linearity are the careful studies of Monroe and French, 6 Suga and Sagawa7, 8 and Weber et al0' 11 in the isolated heart, and of Mahler and co-workers in the conscious animal.9 All of these investigators found precise linearity of end-systolic pressure-volume relations over the physiologic range.…”

The linearity of the end-systolic pressure-volume relationship in man and its sensitivity for assessment of left ventricular function.

“…Ten minutes after the first ventriculogram, 10 mg of isosorbide dinitrate (ISDN) were given sublingually. Arterial pressure was recorded, and when peak systolic pressure had decreased by at least 15 mm Hg, ventriculography was repeated identically.…”

Influence of contractile state on curvilinearity of in situ end-systolic pressure-volume relations.

“…[1][2][3][4][5][6] ESPVR linearity enables a simple description in terms of a slope (Ees) and volume axis intercept (V0) and of a characterization of ventricular contraction by a time-varying elastance model. However, as techniques for ESPVR determination and the condition of experimental preparations have improved, nonlinearity of the relation has been increasingly observed.…”