Effect of postextrasystolic potentiation on amplitude and timing of regional left ventricular wall motion in ischaemic heart disease

Spatio-temporal nonrigid registration for ultrasound cardiac motion estimation

We propose a new spatio-temporal elastic registration algorithm for motion reconstruction from a series of images. The specific application is to estimate displacement fields from two-dimensional ultrasound sequences of the heart. The basic idea is to find a spatio-temporal deformation field that effectively compensates for the motion by minimizing a difference with respect to a reference frame. The key feature of our method is the use of a semi-local spatio-temporal parametric model for the deformation using splines, and the reformulation of the registration task as a global optimization problem. The scale of the spline model controls the smoothness of the displacement field. Our algorithm uses a multiresolution optimization strategy to obtain a higher speed and robustness. We evaluated the accuracy of our algorithm using a synthetic sequence generated with an ultrasound simulation package, together with a realistic cardiac motion model. We compared our new global multiframe approach with a previous method based on pairwise registration of consecutive frames to demonstrate the benefits of introducing temporal consistency. Finally, we applied the algorithm to the regional analysis of the left ventricle. Displacement and strain parameters were evaluated showing significant differences between the normal and pathological segments, thereby illustrating the clinical applicability of our method.

Postextrasystolic potentiation. Do we really know what it means and how to use it?

Postextrasystolic potentiation (PESP), the increase in contractility that follows an extrasystole, is an interesting phenomenon that has been known for almost 100 years. The literature on this effect is reviewed. It is found that there is significant evidence that the phenomenon is independent of muscle loading and represents a distinct property of the myocardium. Examination of the literature pertaining to the cause of the effect suggests that calcium shifts within the sarcoplasmic reticulum are responsible, although there are some conflicts with this conclusion. Regarding the utility of PESP as a diagnostic test of latent viability of ischemic myocardium, the literature review reveals contradictions and conflicts with several methodological problems of the experiments. Finally, concerning the utility of continuous PESP (paired-pacing) to augment ventricular function in the failing ventricle, the studies again are inconclusive and methodologically suspect. Conditions for the proper analysis of the PESP response are reported, and suggestions for future studies are introduced.

Recruitment of a time-dependent inotropic reserve by postextrasystolic potentiation in normal and reperfused myocardium

Impaired excitation-contraction coupling has been suggested as the underlying mechanism of postischemic contractile dysfunction of reperfused myocardium in in-vitro studies. To test this hypothesis in situ, postextrasystolic potentiation (PESP) following an extrasystole with constant prematurity and three different postextrasystolic time intervals (compensated, regular, abbreviated) was analyzed in 12 anesthetized dogs. Changes in regional inotropic state were assessed by comparison of end-systolic wall thickness (sonomicrometry) during PESP to the respective pressure-matched values of an end-systolic pressure/wall-thickness relationship established during brief manual clamping of the aorta. Before ischemia, posterior end-systolic wall-thickness was increased by 0.19 +/- 0.35 (SD) mm during PESP with an abbreviated, by 0.36 +/- 0.42 mm with a regular, and by 0.60 +/- 0.42 mm with a compensated postextrasystolic interval. Baseline systolic wall thickening was decreased from 16.2 +/- 5.4% (before ischemia) to -3.0 +/- 3.4% at the end of 15 min left circumflex coronary occlusion, and to 2.8 +/- 7.5% at 10 min, 7.2 +/- 3.9% at 4 h, and 7.9 +/- 4.1% at 8 h reperfusion. Stepwise increases in regional inotropic state during PESP with increasing postextrasystolic intervals were not different in normal and reperfused myocardium. Thus, excitation-contraction coupling appears not to be impaired during inotropic stimulation of reperfused myocardium in situ.

Right ventricular function 10 years after the Mustard operation for transposition of the great arteries: analysis of size, shape, and wall motion

Biplane right ventriculograms were obtained in 18 symptom free patients 109 (26) months (mean (SD)) after Mustard repair of transposition of the great arteries. Ventricular size, shape, and wall motion were measured from the digitised angiograms and compared with previously published data on left ventricular function after anatomical correction of transposition of the great arteries, with right ventricular function in controls, and with patients before repair of tetralogy of Fallot. Global indices of ventricular function were depressed after Mustard repair and wall motion abnormalities were common. The presence of wall motion abnormalities in this group was associated with a reduction in ejection fraction and ventricular filling rates. In four of five patients in whom an appropriate preoperative angiogram was available a similar pattern of wall motion was seen before the Mustard operation, suggesting that preoperative events may be important in determining eventual outcome.

Changes in left ventricular regional asynchrony after intracoronary thrombolysis in patients with impending myocardial infarction

Ventriculograms obtained before and a mean (SD) of 4.3 (2.5) weeks after intracoronary thrombolysis in 23 patients who were treated within 3.5 (3.1) hours of the onset of pain were examined for changes in asynchronous left ventricular wall motion. Lysis was achieved in 19 patients, and in 16 the affected artery was still patent at restudy. Angiograms were digitised frame by frame. Left ventricular volumes, ejection fraction, and peak ejection rate were all unchanged after thrombolysis, whereas peak filling rate fell, whether or not patency was achieved or maintained. Regional wall motion was examined by means of isometric and contour plots. The area supplied by the affected coronary artery showed simple hypokinesis or akinesis in 10 cases, which was unchanged at the second study in nine and improved in one. The commonest manifestation of asynchrony was delayed inward motion during isovolumic relaxation. This was present in 12 cases with or without associated hypokinesis; after thrombolysis wall motion improved significantly in eight and returned to normal in six, significantly more frequently than it did in patients with simple hypokinesis. Dyskinesis (three patients) and hyperkinesis (five patients) resolved in all. Outward wall motion during isovolumic relaxation reverted to normal in four out of five cases, and outward motion during isovolumic contraction reverted to normal in five out of seven. The frequency of improvement was also increased when the circulation to the affected segment was not compromised by an important residual stenosis. Flow in the affected artery was re-established or maintained significantly less frequently when simple hypokinesis or akinesis was present at the first study. These observations provide further evidence that asynchronous wall motion early after acute myocardial infarction represents residual contractile activity, and suggest that knowledge of its presence and distribution may be useful in assessing patients on whom thrombolysis is performed.

Postextrasystolic potentiation: analysis of methods of induction

Studies were conducted in 15 patients with coronary artery disease to determine if the type of pacing used to induce an extrasystole had a bearing on subsequent postextrasystolic potentiation (PESP) and if the fact that these were evaluated in jeopardized or nonjeopardized portions of the ventricle altered the ability to assess PESP. Two types of pacing were used. In the first group, all beats in the test sequence (basic heart rate, extrasystole, and postextrasystole) were delivered from a programmed external pacemaker. This group was termed the "all-paced" (AP) group, and the postextrasystole was introduced before a compensatory pause could occur, so that loading conditions within the ventricle at the last regular beat and after the extrasystole were not different. In the second group, the extrasystole was coupled to the sensed intrinsic heart rate of the patient, and the postextrasystole was allowed to occur spontaneously. This group was termed the "sensed-paced" (SP) group. Despite differences in basic heart rates and postextrasystolic intervals between the two groups, comparable results were obtained with the two techniques. However, the postextrasystole in the SP group occurred much earlier than expected, probably due to intrinsic cardioacceleration during ventriculography. The net result was that loading conditions in this group before and after the extrasystole were also not different from each other. Results from the pacing techniques were not influenced by whether they were obtained from jeopardized or nonjeopardized segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Postextrasystolic potentiation: regional wall motion before and after revascularization

We evaluated the augmentation of contractility which follows an extrasystole (postextrasystolic potentiation: PESP) in patients before and after coronary revascularization surgery for angina pectoris. PESP was induced by methods which result in essentially identical loading conditions of the ventricle for the beat before the extrasystole and the beat after the extrasystole. We evaluated regional ventricular function before and after revascularization in "jeopardized" segments (supplied by a coronary vessel with significant coronary disease) and "nonjeopardized" segments (supplied by a vessel without significant disease). All coronary lesions were proximal to all three anterior or all posterior segments. Those jeopardized segments with patent grafts which had augmented with PESP improved their baseline function following revascularization. Conversely, those jeopardized segments which failed to augment with PESP decreased their basic function following revascularization. Those segments in which the grafts were occluded failed to augment with PESP after attempted revascularization. Perioperative myocardial infarction resulted in a drop in ejection fraction and a failure to augment with PESP. The nonjeopardized segments responded to PESP similarly to the ischemic augmenting segments. The results of this study suggest that PESP does detect ventricular segments which will improve basic function following revascularization. Those segments which fail to augment with PESP are most likely more ischemic than the augmenting segments, will not improve, and may even decrease function following revascularization.