Effects of uncomplicated coronary artery bypass graft surgery on global and regional left ventricular function at rest. Study by equilibrium radionuclide angiocardiography

The Postoperative Paradoxical Septum (POPS): A Comprehensive Review on Physio-Pathological Mechanisms

The interventricular septum (IVS) is a core myocardial structure involved in biventricular coupling and performance. Physiologically, during systole, it moves symmetrically toward the center of the left ventricle (LV) and opposite during diastole. Several pathological conditions produce a reversal or paradoxical septal motion, such as after uncomplicated cardiac surgery (CS). The postoperative paradoxical septum (POPS) was observed in a high rate of cases, representing a unicum in the panorama of paradoxical septa as it does not induce significant ventricular morpho-functional alterations nor negative clinical impact. Although it was previously considered a postoperative event, evidence suggests that it might also appear during surgery and gradually resolve over time. The mechanism behind this phenomenon is still debated. In this article, we will provide a comprehensive review of the various theories generated over the past fifty years to explain its pathological basis. Finally, we will attempt to give a heuristic interpretation of the biventricular postoperative motion pattern based on the switch of the ventricular anchor points.

Reverse Septal Movement: A Step Forward in the Comprehension of the Underlying Causes

(1) Background: Reverse septal movement (RSM) often occurs after cardiac surgery, consisting of a paradoxical systolic movement of the interventricular septum. In this retrospective study, we aimed to investigate possible determinants of RSM after coronary artery bypass surgery (CABG). (2) Methods: Patients who underwent CABG with on- or off-pump techniques at our center from March 2019 to October 2021 were retrospectively included. Exclusion criteria were: exposure to combined procedures (e.g., valve implantation), prior cardiac surgery, intraventricular conduction delays, and previous pacemaker implantation. Laboratory tests and echocardiographic and cardiopulmonary bypass (CPB) duration data were collected. (3) Results: We enrolled 138 patients, of whom 32 (23.2%) underwent off-pump CABG. Approximately 89.1% of the population was male; the mean age was 70 ± 11 years. There was no difference in RSM incidence in patients undergoing the off-pump and on-pump techniques (71.9% vs. 62.3%; p = 0.319). In patients undergoing on-pump surgery, the incidence of RSM was slightly higher in longer CPB procedures (OR 1.02 (1.00-1.03) p = 0.012), and clamping aortic time was also greater (OR 1.02 (1.00-1.03) p = 0.042). (4) Conclusions: CPB length seems to be correlated with a higher RSM appearance. This better knowledge of RSM reinforces the safety of CABG and its neutral effect on global biventricular function.

Echocardiographic investigation of the mechanism underlying abnormal interventricular septal motion after open heart surgery

Background

Abnormal interventricular septal motion (ASM) is frequently observed after open heart surgery (OHS). The aim of this study was to investigate the incidence and temporal change of ASM, and its underlying mechanism in patients who underwent OHS using transthoracic echocardiography (TTE).

Methods

In total, 165 patients [60 ± 13 years, 92 (56%) men] who underwent coronary bypass surgery or heart valve surgery were consecutively enrolled in a prospective manner. TTE was performed preoperatively, at 3--6-month postoperatively, and at the 1-year follow-up visit. Routine TTE images and strain analysis were performed using velocity vector imaging.

Results

ASM was documented in 121 of 165 patients (73%) immediately after surgery: 26 patients (17%) presented concomitant expiratory diastolic flow reversal of the hepatic vein, 11 (7%) had inferior vena cava plethora, and 11 (7%) had both. Only 2 patients (1%) showed clinically discernible constriction. ASM persisted 3--6 months after surgery in 38 patients (25%), but only in 23 (15%) after 1 year. There was no difference in preoperative and postoperative peak systolic strain of all segments of the left ventricle (LV) between groups with or without ASM. However, systolic radial velocity (V_Rad) of the mid anterior-septum and anterior wall of the LV significantly decreased in patients with ASM.

Conclusion

Although ASM was common (74%) immediately after OHS, it disappeared over time without causing clinically detectable constriction. Furthermore, we consider that ASM might not be caused by myocardial ischemia, but by the decreased systolic V_Rad of the interventricular septum after pericardium incision.

Abnormal motion of the interventricular septum after coronary artery bypass graft surgery: comprehensive evaluation with MR imaging

OBJECTIVE

To define the mechanism associated with abnormal septal motion (ASM) after coronary artery bypass graft surgery (CABG) using comprehensive MR imaging techniques.

MATERIALS AND METHODS

Eighteen patients (mean age, 58 ± 12 years; 15 males) were studied with comprehensive MR imaging using rest/stress perfusion, rest cine, and delayed enhancement (DE)-MR techniques before and after CABG. Myocardial tagging was also performed following CABG. Septal wall motion was compared in the ASM and non-ASM groups. Preoperative and postoperative results with regard to septal wall motion in the ASM group were also compared. We then analyzed circumferential strain after CABG in both the septal and lateral walls in the ASM group.

RESULTS

All patients had normal septal wall motion and perfusion without evidence of non-viable myocardium prior to surgery. Postoperatively, ASM at rest and/or stress state was documented in 10 patients (56%). However, all of these had normal rest/stress perfusion and DE findings at the septum. Septal wall motion after CABG in the ASM group was significantly lower than that in the non-ASM group (2.1±5.3 mm vs. 14.9±4.7 mm in the non-ASM group; p < 0.001). In the ASM group, the degree of septal wall motion showed a significant decrease after CABG (preoperative vs. postoperative = 15.8±4.5 mm vs. 2.1±5.3 mm; p = 0.007). In the ASM group after CABG, circumferential shortening of the septum was even larger than that of the lateral wall (-20.89±5.41 vs. -15.41±3.7, p < 0.05)

CONCLUSION

Abnormal septal motion might not be caused by ischemic insult. We suggest that ASM might occur due to an increase in anterior cardiac mobility after incision of the pericardium.

Case report: paradoxical ventricular septal motion in the setting of primary right ventricular myocardial failure

PURPOSE

In this report, a case of right ventricular (RV) failure, hemodynamic instability, and systemic organ failure is described to highlight how paradoxical ventricular systolic septal motion (PVSM), or a rightward systolic displacement of the interventricular septum, may contribute to RV ejection.

CLINICAL FEATURES

Multiple inotropic medications and vasopressors were administered to treat right heart failure and systemic hypotension in a patient following combined aortic and mitral valve replacement. In the early postoperative period, echocardiographic evaluation revealed adequate left ventricular systolic function, akinesis of the RV myocardial tissues, and PVSM. In the presence of PVSM, RV fractional area of contraction was > or =35% despite akinesis of the primary RV myocardial walls. The PVSM appeared to contribute toward RV ejection. As a result, the need for multiple inotropes was re-evaluated, in considering that end-organ dysfunction was the result of systemic hypotension and prolonged vasopressor administration. After discontinuation of phosphodiesterase inhibitors, native vascular tone returned and the need for vasopressors declined. This was followed by recovery of systemic organ function. Echocardiographic re-evaluation two years later, revealed persistent akinesis of the RV myocardial tissues and PVSM, the latter appearing to contribute toward RV ejection.

CONCLUSIONS

This case highlights the importance of left to RV interactions, and how PVSM may mediate these hemodynamic interactions.

Mechanism of paradoxical ventricular septal motion after coronary artery bypass grafting

Paradoxical septal motion is commonly noted on echocardiography after coronary artery bypass grafting (CABG), but its mechanism is unclear. Cardiac magnetic resonance imaging was performed before and 3 months after CABG in 23 patients. On a mid-left ventricular short-axis cine image, the motion of myocardial landmarks during the cardiac cycle was ascertained relative to a stationary anterior reference point. Before CABG, the movement of the ventricular septum in systole was either posterior or neutral (median -2 mm) in 19 patients, whereas after CABG, the septum moved anteriorly in all 23 patients (+4 mm; p<0.001). (A positive sign indicates anterior motion in ventricular systole, and a negative sign denotes posterior motion.) The motion of the right ventricular free wall was reduced after CABG (-5 vs -3 mm; p=0.002), whereas anterior movement of the lateral left ventricular wall in systole increased (+4 vs +9 mm; p<0.001). There was a positive correlation between degree of anterior movement of the ventricular septum and right ventricular ejection fraction (r=0.47, p=0.023). In conclusion, after CABG, the entire left ventricle translocated anteriorly in systole. Despite preserved right ventricular function, there was restricted motion of the right ventricular free wall suggestive of postoperative adhesions. The pattern of movement observed offers a sound explanation for postoperative paradoxical septal motion.

Automatic quantitation of regional myocardial wall motion and thickening from gated technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography

OBJECTIVES

We developed an automatic quantitative algorithm for the measurement of regional myocardial wall motion and wall thickening from three-dimensional gated technetium-99m sestamibi myocardial perfusion single-photon emission computed tomographic images.

BACKGROUND

The algorithm measures the motion of the three-dimensional endocardial surface using a modification of the centerline method, as well as wall thickening using both geometry (gaussian fit) and partial volume (counts).

METHODS

The algorithm was tested using a "variable thickness" heart phantom, and the quantitative results were compared with visual segmental assessment of myocardial motion and thickening in 79 clinical patients with a wide range of ejection fractions (6% to 87%).

RESULTS

Phantom measurements of simulated motion and thickening were accurate regardless of the camera used (dual or triple detector), the angular span of reconstructed data (180 degrees or 360 degrees), the amount of motion (3 or 6 mm) or the amount of thickening (33%, 50% or 100%). Quantitative measurements of segmental motion and thickening in the patients were correlated with visual scores (r = 0.668, exact agreement 72.6%, kappa 0.433 and r = 0.550, exact agreement 74.7%, kappa 0.408, respectively). Significant inverse linear relations exist between the global (summed) visual motion score and the average quantitative motion, and between the global (summed) visual thickening score and the average quantitative thickening. Automatic quantitative ejection fraction measurements correlated extremely well with average quantitative motion (r = 0.929) and thickening (r = 0.959).

CONCLUSIONS

Our algorithm is accurate and may be the first automatic technique for the quantitative three-dimensional assessment of regional ventricular function in cardiology.