H.J.C. Swan

Measurement of Coronary Sinus Blood Flow by Continuous Thermodilution in Man

A technique was developed for measurement of blood flow in the coronary sinus in man by continuous thermodilution. For single determinations, 5% dextrose at room temperature is injected at a constant rate of 35 ml/min for a period of about 20 sec. In 14 subjects with normal coronary arteries the mean coronary sinus blood flow was 122 ± 25 ml/min (range, 83 to 159 ml/min). The blood flow computed per 100 g of left ventricle was 82 ± 16 ml/min, which is in the range of values obtained by nitrous oxide and coincidence counting methods. In 35 patients with arteriographically confirmed coronary artery disease the mean flow was similar (128 ± 20 ml/min; range, 92 to 167 ml/min).A special catheter was used for simultaneous measurement of blood flow in the coronary sinus and great cardiac vein. In eight normal subjects the mean great cardiac vein flow was 68 ± 11 ml/min (range, 51 to 78 ml/min) or 65 ± 10% of the coronary sinus blood flow. The method allowed continuous measurement of flow over a period of several minutes and, for the first time, measurement of rapid changes in myocardial perfusion.

A new technique for measurement of cardiac output by thermodilution in man

Abstract A technique for measurement of cardiac output by thermodilution (COTD) in man has been described. Comparison with cardiac outputs determined simultaneously by the dye-dilution technique (CODYE) in 63 measurements in 20 patients showed close agreement of the 2 methods in a range of values from 2.9 to 8.0 liters/min (COTD = 0.96 CODYE + 0.2, r = 0.96). The reproducibility of measurements was 4.1 percent with the thermodilution and 5.4 percent with the dye-dilution technique. The thermodilution technique does not require withdrawal of blood during measurements and removal of blood for calibration. The calibration is simple and accurate. There is virtually no recirculation, so that a simple integrator can be used for determination of the area beneath the thermodilution curve.

Thermodilution cardiac output determination with a single flow-directed catheter.

Abstract A single right heart catheter which allows simultaneous determinations of cardiac output, pulmonary artery pressure, pulmonary capillary wedge pressure, and right atrial pressure in critically ill patients is described. The catheter, which utilizes the thermodilution technique of cardiac output determination, may be rapidly and safely passed at the bedside without fluoroscopy.

Correlative classification of clinical and hemodynamic function after acute myocardial infarction

To characterize the relation between clinical and hemodynamic state in acute myocardial infarction, 200 patients with acute infarction were evaluated with clinical and hemodynamic criteria. Patients were classified clinically on the basis of peripheral hypoperfusion (hypotension, tachycardia, confusion, cyanosis, oliguria) and pulmonary congestion (rales, abnormal chest roentgenogram). Four clinical subsets were defined that correlated with cardiac index (Cl, liters/min per m2) and pulmonary capillary pressure (PCP, mm Hg): (see article). Parallel hemodynamic subsets were developed independently on the basis of depressed cardiac index (2.2 liters/min per m2 or less) and elevated pulmonary capillary pressure (greater than 18 mm Hg). The rate of accuracy of clinical examination in predicting hemodynamic abnormalities was 83 percent. Mortality rates were similar in the clinical and hemodynamic subset calssifications, averaging 2.2 percent in subset I, 10.1 percent in subset II, 22.4 percent in subset III and 55.5 percent in subset IV. Drug interventions in the course of hospitalization resulted in a 38 percent increase in depressed cardiac index and 34 percent decrease in elevated pulmonary capillary pressure. Resolution of clinical abnormalities paralleled this hemodynamic improvement in 70 percent of patients. These data suggest that clinical performance and both clinical and hemodynamic subsets are directly relevant to establishing prognosis and the selection of therapy in patients with acute myocardial infarction.

Measurement of blood flow by thermodilution

Abstract In thermodilution a known change in heat content of the blood is induced at one point of the circulation and the resultant change in temperature detected at a point downstream. When cardiac output is measured, a bolus of cool liquid is injected into the upper right atrium and the temperature change detected in the pulmonary artery. When flow in single blood vessels is measured, the distance between the site of injection and the site of detection is small; therefore, mixing must be attained by the kinetic energy of the injectate. The continuous constant rate injection technique is most suitable for measurement of venous flow. Since the blood flow in arteries can be markedly and unpredictably altered by the injection or the injectate, this technique is not suitable to measure flow in arteries. Measurement of venous flow by the bolus injection technique is tedious and time-consuming because of the complex formula. Minimal recirculation, simple and accurate calibration, intravascular detection of temperature and simple equipment are the advantages of the thermodilution technique.

Beneficial Effects of Vasodilator Agents in Severe Mitral Regurgitation Due to Dysfunction of Subvalvar Apparatus

To assess the potential beneficial effects of vasodilator agents in patients with severe mitral regurgitation, sodium nitroprusside was administered intravenously at a rate of 16 to 100 μg/min in eight patients with clinically significant mitral regurgitation presumably due to dysfunction of the subvalvar apparatus. In all patients there was a decrease in the magnitude of the peak ‘V’ wave (from 50 ± 4.5 to 19 ± 2.9 mm Hg) and in left ventricular filling pressure (33 ± 1.8 to 16 ± 1.4 mm Hg), together with a decreased intensity of the apical pansystolic murmur. There was a significant increase in forward cardiac index (2.2 ± 3.5 to 3.3 ± .47 liter/min/M2) and forward stroke volume index (23 ± 4.4 to 36 ± 6.6 ml/M2) along with a reduction in systemic vascular resistance (1802 ± 331 to 1102 ± 241 dynes/sec/cm-5). In the five patients in whom the therapy was continued, relief of symptoms of pulmonary venous congestion occurred. In the four patients in whom left ventricular volumes were determined angiographically, the observed increase in forward stroke volume was due to a reduction in the regurgitant fraction. These findings suggest that the use of vasodilator agents like nitroprusside can achieve the major objectives of treatment of patients with mitral regurgitation: an increase in forward stroke output, a reduction in regurgitant volume and a decrease in pulmonary venous pressure.

Influence of Direct Myocardial Revascularization on Left Ventricular Asynergy and Function in Patients with Coronary Heart Disease With and without Previous Myocardial Infarction

The influence of successful aortocoronary artery bypass surgery on left ventricular asynergy and dysfunction was studied by hemodynamic and angiographic methods in 29 patients with coronary artery disease. Eight patients had the preinfarction syndrome, 10 patients had chronic ischemia without previous infarction, and 11 patients had chronic ischemia with previous infarction. LV asynergy was present preoperatively in 12 of the 18 patients in the first two groups. Marked improvement occurred in all and a normal wall motion was restored in the majority following surgery. More pronounced improvement was noted in the preinfarction syndrome as compared to the group with chronic ischemia and no previous infarct. The ejection fraction was reduced in 12 of the 18 patients in these two groups and significant improvement was observed postoperatively [0.45 ± 0.03 (SEM) to 0.74 ± 0.03]. Increase in ejection fraction was primarily due to a decrease in the end-systolic volume (71 ± 12 to 23 ± 4 ml/m2). The end-diastolic volume was only slightly reduced (114 ± 12 to 97 ± 9 ml/m2). Left ventricular end-diastolic pressure fell from 15 ± 1 to 10 ± 1 mm Hg.In nine of 11 patients who had previous myocardial infarction, abnormal wall motion was present preoperatively. Following surgery, some abnormalities of wall motion persisted in the areas of known infarction, although significant improvement of wall motion occurred in the noninfarcted segments. The ejection fraction was reduced in seven of these 11 patients and improved postoperatively. (0.44 ± 0.05 to 0.59 ± 0.05). The end-systolic volume decreased from 57 ± 5 to 41 ± 6 ml/m2, and the end-diastolic volume was unchanged (106 ± 5 to 108 ml/m2). Left ventricular end-diastolic pressure fell from a mean value of 17 ± 3 to a mean value of 10 ± 2 mmHg following successful surgery. These findings are consistent with improved pump function and were associated with improvement in indices of contractile state. The observations indicate that significant improvement in ventricular wall motion and pump function occurs in patients with obstructive coronary disease following successful aortocoronary artery bypass surgery even in the presence of old myocardial infarction. Since the patients of the present study all had normal initial end-diastolic volumes, however, similar beneficial results might not occur in patients with cardiomegaly and more severe heart failure.

Hemodynamic Spectrum of Myocardial Infarction and Cardiogenic Shock A Conceptual Model

Despite the recent accumulation of a large hemodynamic data base describing myocardial infarction and cardiogenic shock, precise characterization of patient subsets has been elusive. This paper represents an attempt to identify the major factors contributing to this wide hemodynamic spectrum, and their interrelation using a theoretical model based upon currently emerging concepts of this disease. It is proposed that the hemodynamic alterations associated with acute infarction are a consequence both of reduction in contractile mass and alteration in left ventricular compliance. In addition, mitral insufficiency, altered contractility, and the peripheral circulation interact to produce wide divergence between clinical and hemodynamic features from case to case and during the progression of the course of the illness. This model may more rationally explain the genesis and natural history of “heart failure’ and the “shock syndrome’ associated with acute myocardial infarction and in addition explain the extremely variable responses to both drug therapy and to more aggressive modes of treatment of power failure.

Effects of Isometric Exercise on Cardiac Performance The Grip Test

Twenty-two patients with heart disease performed a standard isometric exercise, sustained handgrip, during the course of diagnostic cardiac catheterization. During handgrip an increase in mean arterial pressure (average 87 to 104 mm Hg) was noted in all patients. Coronary sinus blood flow and myocardial O2 consumption increased (average 45%) in all patients so monitored. Systemic vascular resistance increased in 19 patients, in contrast to the response reported in normal volunteers. The relation between left ventricular stroke-work index and LVEDP (left ventricular function curve) during the control state and during the fourth minute of sustained handgrip provided a simple estimate of left ventricular reserve and correlated well with the New York Heart Association functional classification of the patient studied. Patients with good reserve had a rise in stroke-work with little or no change in LVEDP. Patients with poor reserve had a fall in stroke-work together with a substantial rise in LVEDP. It is concluded that the stress imposed by sustained handgrip provides a simple test for the evaluation of left ventricular reserve.

Early changes in regional and global left ventricular function induced by graded reductions in regional coronary perfusion

To determine the sequence of changes in segmental myocardial function, regional lactate metabolism and global left ventricular function induced by mild regional ischemia, blood flow in the left anterior descending coronary artery of 10 dogs was reduced by 10 percent decrements with use of a screw clamp. At each level of flow, segmental mechanical function and regional metabolism were assessed, the former with use of a mercury-in-Silastic length gauge and the latter with transmyocardial lactate balance measurements obtained with sampling from the anterior interventricular vein. Coronary arterial flow at the onset of regional lactate production was 48 +/- 4 percent (mean +/- standard error of the mean) of the control value. The onset of segmental mechanical dysfunction coincided with the onset of lactate production. Epicardial S-T segment abnormalities over the ischemic zone usually could not be detected until coronary flow was further reduced. After the onset of regional ischemia there was a linear correlation between coronary arterial flow and regional lactate production. At the onset of mild regional ischemia, defined as the onset of regional lactate production, no significant or directionally consistent changes were noted in standard measurements of global left ventricular performance, including heart rate, mean aortic pressure, left ventricular end-diastolic pressure, cardiac output, stroke volume, stroke work and peak positive dP/dt (maximal rate of rise of pressure). However, peak negative dP/dt (maximal rate of pressure decrease) decreased from 99 +/- 2 to 89 +/- 3 percent of the control value (P less than 0.0005) coincident with the onset of ischemia. It is hypothesized that dyssynchronous wall motion in the ischemic zone during isometric relaxation accounts for this decrease in peak negative dP/dt.