Three-dimensional analysis of regional myocardial function in response to nitroglycerin in patients with coronary artery disease.

Biplane cineventriculography was performed at rest and after sublingual nitroglycerin in 13 patients with coronary artery disease. In six patients (responders), there was a significant increase in ejection fraction [40 +/- 5 to 52 +/- 4% (p less than 0.001)], while in the other seven (nonresponders), there was no alteration in ejection fraction. To evaluate the extent of regional myocardial response to nitroglycerin, the contractile pattern of the regional myocardium over the entire ventricular surface was analyzed using a computer-generated three-dimensional model. The spatial coordinates that define the elliptic ventricular surface on a given horizontal plane cross section of the chamber were determined by four counter values in the two orthogonal silhouettes. Then, 32 points at equal angles around the center of gravity of the end-diastolic cavity were generated to form the border image. Repetition of this process for 16 successive cross sections allowed for reconstruction of the ventricular surface by the sequence of 32 X 16 (512) points. The regional wall motion was expressed as the percent change of the radial length, drawn from the center of gravity to each surface point. There was significant heterogeneity in regional response to nitroglycerin. In the responders, the normally contracting area was significantly increased (from 16.5 +/- 16.0 to 36.2 +/- 14.9% of the total surface area, p less than 0.001), largely mediated by the greater improvement in segmental shortening of each graded contractile pattern relative to its deterioration. In the nonresponders, a lessening of the severe dysfunction of the given area was associated with significant deterioration of segmental shortening of the other normally contracting area (49.1 +/- 19.7% of the area with a contractile pattern of grade 5 had deteriorated, p less than 0.05). Thus, the ratio of the area with respective graded segmental shortening was virtually unchanged. These differences in response of the ischemic ventricle to nitroglycerin appeared to be related to the development of adequate coronary collateral vessels as well as to an interaction of changes in preload and afterload.

Changes in diastolic properties of the regional myocardium during pacing-induced ischemia in human subjects.

Mechanisms related to alterations in the diastolic properties of the left ventricle during angina were studied in seven patients with coronary artery disease. Single plane left ventriculograms were obtained using a high fidelity micromanometer-tipped catheter in both the resting state and immediately after rapid cardiac pacing. In all patients, typical anginal pain developed with pacing stress. After atrial pacing, the left ventricular end-diastolic pressure increased from 10 +/- 3 to 21 +/- 7 mm Hg (+/- standard deviation) (p less than 0.005) regardless of the changes in the end-diastolic volume. The ejection fraction was reduced from 59 +/- 10 to 48 +/- 13% (p less than 0.05). The diastolic pressure-volume curves shifted upward in post-pacing beats in four patients, while in three the curves shifted more to the right. The regional myocardial function was expressed in quantitative terms by a radial coordinate system with the origin at the center of gravity of the end-diastolic silhouette. Two representative radial grids for normal and ischemic segments were selected. In the normal segment, the end-diastolic length was augmented by 15% (p less than 0.005) and was associated with a 24% increase in stroke excursion with pacing stress (p less than 0.05). The increase in diastolic pressure was accompanied by comparable increases in end-diastolic length, and the diastolic pressure-length relation moved up to the higher portion of the single curve. In the ischemic segment, the end-diastolic length remained unchanged in the post-pacing beat, but segment shortening was significantly reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of asynchronous wall motion by regional pressure-length loops in patients with coronary artery disease.

The progression of regional dysfunction during angina pectoris was studied in eight patients with coronary artery disease. Single plane left ventriculograms were obtained using a high fidelity micromanometer-tipped catheter both at rest and immediately after rapid cardiac pacing. Each image of the left ventriculogram was digitized and transferred to a computer. The boundary of the ventricular cavity was automatically determined and sequentially superimposed. Regional shortening was quantified by a radial coordinate system originating at the center of gravity of the end-diastolic silhouette. Thirty-two radial grids were drawn around the center of gravity, and the length of each radial grid was measured to characterize the centripetal motion of a given surface point. Each radial length was then plotted simultaneously and continuously against left ventricular pressure to generate a pressure-length loop. The area of the pressure-length loop provided an index of regional myocardial work. In the ischemic ventricle, the loops exhibited a striking deformity in configuration. Prolonged relaxation of ischemic segments was associated with outward motion of the normal segments. Shortening of the normal segment occurred earlier than that of the ischemic segment associated with its stretch. Thus, the loops of the two areas inclined in opposite directions. Pacing stress increased the magnitude of hypofunction in the potentially ischemic area, the average extent of shortening being reduced by 30% and the segmental work by 25% (p less than 0.005). In the normal area, contrary to the significant increase in segmental shortening (20% above control values [p less than 0.005]), the average segmental work remained at 7% below control values because of an augmented deformation of the loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of posture on cardiac autonomic nervous activity in patients with congestive heart failure.

OBJECTIVES: We aimed to clarify which recumbent position is preferred by patients with congestive heart failure (CHF) and to evaluate whether cardiac autonomic nervous activity is different among three recumbent positions (supine, left lateral decubitus, right lateral decubitus) in patients with CHF. BACKGROUND: It remains unclear whether cardiac autonomic nervous activity is different among three recumbent positions in patients with CHF. METHODS: We studied 17 male CHF patients (66+/-7 years) and 17 age- and gender-matched healthy subjects (66+/-7 years). Each subject underwent 24-h ambulatory electrocardiographic monitoring. A channel was used to record the CM5 lead, and another to record the signal of the patient's posture with use of a newly developed small-sized detector (3.2 cm x 3.2 cm). By using spectral analysis of heart rate variability, frequency-domain measures were calculated and compared among the three recumbent positions. Normalized high-frequency (HF: 0.15 to 0.40 Hz) power was used as an index of vagal activity and the low frequency (0.04 to 0.15 Hz)/HF power ratio was used as an index of sympathovagal balance. RESULTS: In patients with CHF, the time for the right lateral decubitus position was two-fold longer than that for the supine and left lateral decubitus positions. The increased cardiac sympathetic activity and decreased vagal tone in CHF patients were normalized in the right lateral decubitus position. CONCLUSIONS: The right lateral decubitus position in patients with CHF may be a self-protecting mechanism of attenuating the imbalance of cardiac autonomic nervous activity.

Automated method for left ventricular volume measurement by cineventriculography with minimal doses of contrast medium.

Cineventriculography is of considerable value in the dimensional analysis of the left ventricular cavity, but conventional methods necessitate injection of large amounts of contrast medium. In this study, small dose left ventriculography, using only 5 ml of dye, was performed in order to minimize the untoward effects of contrast medium. A computer-aided image processing system was also developed to enhance the contrast of the ventricular image by subtracting the reference image to eliminate irrelevant background. The boundary of the left ventricular cavity was automatically determined to calculate the instantaneous volume change throughout the cardiac cycle. With use of this small dose of dye, the elevation of left ventricular end-diastolic pressure that consistently occurred 1 to 3 minutes after injection of conventional large doses could be avoided. (End-diastolic pressure at 1 minute after dye injection averaged 11.8 +/- 4.9 [mean +/- standard deviation] for small dose and 19.1 +/- 6.1 mm Hg for large dose injection.) Values for end-diastolic volume, end-systolic volume and ejection fraction calculated from the two consecutive small and large dose left ventriculograms in 16 patients were similar. Thus, minimal doses of contrast medium permit accurate measurement of left ventricular dimension and function without significant hemodynamic derangement. The optimal projection for regional wall motion analysis can easily be selected by this method with repeated exposure at various degrees of obliquity. With this technique, even noninvasive measurement of left ventricular volume can be provided by intravenous injection of small doses of contrast agent.

3-D heart image reconstructed from MRI data.

The gated MRI method gives us several sets of cross-sectional images on transverse, coronal, and sagittal planes of the heart in a cardiac cycle. In this paper, a method to reconstruct 3-D shapes of each part of the heart (i.e., left ventricle, left atrium, right ventricle, right atrium, aorta, and pulmonary artery), in a voxel space using these sets of cross-sectional images is proposed. The whole heart image composed of these six parts properly put together can be superimposed on the original cross-sectional images for display purposes.

[Pathophysiological analysis of cardiac function by computer processing of echocardiograms].

Automatic image processing system has been developed for analysis of cardiac function with echocardiograms. Echograms of apical long axis view were transferred to microcomputer system and processed to display three dimensional images of left ventricular myocardium. With this technology, analysis of left ventricular wall thickness in three dimensional manner revealed pathophysiological changes in ischemic heart disease.

Left ventricular image processing.

Left ventricular image processing methods of x-ray cineangiocardiograms and ultrasound echocardiograms are discussed. 3-D reconstruction methods of the left ventricle from ultrasound echocardiograms and magnetic resonance images are also discussed. Boundary detection of the left ventricle and the quantitative analysis of the left ventricular function and wall motion are discussed. To reconstruct 3-D shapes, we need several cross sectional shapes or silhouettes of the left ventricle. Several cross sectional echo images of apical long axis view are taken by changing the angles of rotation of the probe of echo transducer around its axis. Gated multi-phase MRI method is used to obtain each 2 cross sectional images in transverse, coronal and sagittal directions. Some results of 3-D shapes of the left ventricle and myocardium reconstructed are shown and 3-D functional images which give us regional functions of the left ventricular wall on three dimensional shape are shown.

Left ventricular image processing of 2-D echocardiograms and 3-D reconstruction of the left ventricle.

Image processing systems of echocardiograms are discussed. The left ventricular boundary on every 2-D echocardiogram on consecutive frames digitized with an ECG (electrocardiogram) signal is traced automatically after initial manual drawing of the boundary on an end diastolic image. Various cardiac parameters are derived from these left ventricular boundaries over a cardiac cycle: volume change, regional wall motion, percentage shortening of regional wall and so on. 3-D shapes of the left ventricle and myocardium are reconstructed from several sequences of cross-sectional echo data. Cardiac parameters are also derived from these 3-D shapes and are shown on 3-D shapes as functional images of 3-D left ventricle.

Effects of posture on sympathetic nervous modulation in patients with chronic heart failure.

We investigated which recumbent position is preferred by patients with chronic heart failure (CHF) and whether sympathetic nervous modulation differs in three recumbent positions. We assessed 12 patients with CHF by spectral analysis of heart-rate variability and measurement of plasma norepinephrine concentrations. The right lateral decubitus position was preferred for significantly longer periods than the left lateral decubitus and supine positions. Sympathetic nervous modulation was most attenuated in the right lateral decubitus position. The right lateral decubitus position preferred by patients with CHF may be a self-protective mechanism to control increased sympathetic nervous modulation.

[Assessment of cardiac function by left heart catheterization: an analysis of left ventricular pressure-volume (length) loops].

The mechanical property of the cardiac muscle has been classically analyzed in two ways; shortening of muscle fiber, and the development of tension within the muscle. In the ejecting ventricle, left ventricular (LV) function can be analyzed by the analogous two-dimensional framework of pressure-volume loops, which are provided by plotting the instantaneous volume against corresponding LV pressure. The integral pressure with respect to volume allows to assess a total external ventricular work during ejection. The diastolic pressure-volume relations reflect a chamber stiffness of the ventricle. Force-velocity relations also provide an useful conceptual framework for understanding how the ventricle contracts under given afterload, with modification of preload. In the presence of coronary artery disease, the regional nature of left ventricular contractile function should be defined as well as the global ventricular function as described above, because the latter is determined by the complex interaction of dysfunction of the ischemic myocardium and of compensatory augmentation of shortening of the normally perfused myocardium. We utilized a computer technique to analyze the local wall motion of the ischemic heart by cineventriculography. The boundaries of serial ventricular images are automatically traced and superimposed using the external reference system. Radial grids are drawn from the center of gravity of the end-diastolic image. Measurement of length of each radial grid throughout cardiac cycle provides the analysis of movement of the ventricle at a particular point on the circumference. Using phasic pressure obtained simultaneously with opacification as the common parameter, segmental pressure-length loops are constructed simultaneously at various segments. The loops are similar over the entire circumference in the normal heart, being rectangular in morphology and with synchronous behavior during contraction and relaxation. However, the marked distortion of pressure-length loops with clockwise rotation or figure of eight inscription is observed in the ischemic segments. Systolic work of the ischemic segment diminishes dramatically, and the loops exhibit varying degrees of inclination. The control segment loops also show an inclination to the opposite direction of the ischemic loops. These differences are presumably related to the local redistribution of the myocardial tension during systole in the ischemic ventricle. Thus, the method described should be of particular value in assessing the regional myocardial function in the ischemic ventricle and effects of various interventions which modify ischemia.

Intravenous left ventriculography utilizing digital subtraction technique.

To detect the left ventricular boundary in the intravenous ventriculography, we used a subtraction technique for background suppression. Images containing contrast medium and reference mask images were transferred to a computer through a flying spot scanner and stored on the digital disc. Stored reference mask images were subtracted from the digitized contrast images. The resulting images were then electronically enhanced to extract the left ventricular (LV) image. The LV boundary was delineated with an algorithm we have developed and the volume of the LV cavity was calculated automatically. The validity of this method was compared with data obtained from conventional left ventriculogram (LVG). In 11 patients, values for end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) calculated from the intravenous LVG were correlated closely with those from the conventional LVG (128 +/- 38 (SD) vs 133 +/- 39 ml, r = 0.95; 50 +/- 28 vs 53 +/- 30 ml, r = 0.98; 63 +/- 10 vs 62 +/- 12%, r = 0.96, respectively). Nine patients with valvular regurgitation were followed up serially after valve replacement. EDV index fell significantly after corrective surgery (145 +/- 50 to 81 +/- 33 ml/m2, p less than 0.02), whereas, EF was affected variably depending upon the preoperative state (58 +/- 13 to 61 +/- 11%, not significant). Thus, this method is less invasive than conventional LVG and has successfully allowed for sequential determination of ventricular function on an outpatient basis.

Modification of pacing-induced alterations in diastolic properties of the regional myocardium by nifedipine in patients with coronary artery disease.

The effects of nifedipine on regional dysfunction during pacing-induced ischemia were studied in eight patients with coronary artery disease. Single-plane left ventriculograms were obtained using a high-fidelity micromanometer-tipped catheter in the control and post-pacing periods both before and after pretreatment with nifedipine. All patients developed typical anginal pain during pacing tachycardia before but not after pretreatment with nifedipine. After pacing, left ventricular end-diastolic pressure (EDP) increased from 10 +/- 5 (SD) mmHg to 23 +/- 9 mmHg (P less than 0.01) with enlargement of the end-diastolic volume (EDV). The ejection fraction (EF) was reduced from 66 +/- 10% to 54 +/- 13% (P less than 0.05). With nifedipine, a post-pacing increase in EDP was markedly attenuated together with a 17% reduction in left ventricular systolic pressure (P less than 0.05). The regional myocardial function was expressed by a radial coordinate system with its origin at the center of gravity of the end-diastolic contour. Two representative radial grids for normal and ischemic segments were selected. In the normal segment, the end-diastolic length (EDL) was augmented by 14% (from 26.1 +/- 5.2 mm to 29.7 +/- 6.1 mm, P less than 0.01) associated with a 23% increase in stroke excursion (P less than 0.05) with pacing stress. In the ischemic segments, EDL remained unchanged in the post-pacing beat but stroke excursion was significantly reduced (from 11.4 +/- 5.2 mm to 4.3 +/- 1.8 mm, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)