Contradictory Shear Stress Distribution Prevents Restenosis after Provisional Stenting for Bifurcation Lesions

Background: Endothelial shear stress is one of the local hemodynamic factors suspected in the development of coronary atherosclerosis in bifurcation lesions. In patients with provisional stenting, the endothelial shear stress (SS) distribution is unknown. Objective: The aim of this study was to investigate the magnitude and distribution of the SS of coronary bifurcation lesions stenting by the provisional approach. Methods: Ten consecutive patients were included in this study. Quantitative coronary analysis, flow study, and three‐dimensional computational analysis with the aid of the commercial software CD STAR‐CCM+ were done before and after the provisional stenting procedure and also 8 months later. Results: Clinical and angiographic follow‐up were available in all patients. No patient had a side branch (SB) stent. At the 8‐month follow‐up, no major adverse cardiac event (MACE) occurred. There was also no clinical and angiographic restenosis. Before PCI, the distal main vessel (MV)‐lateral, and the SB‐lateral subsegments had relative nonsignificant lower SS value (4.08 ± 2.78 Pa and 4.35 ± 5.04 Pa, respectively) when compared to other segments. After 8‐month follow‐up, sustained decreased SS value was shown in the distal MV‐lateral segment (4.08 ± 2.78–1.68 ± 1.65 Pa), when compared with significantly increased SS value in the SB‐lateral subsegment 4.35 ± 5.04–16.50 ± 40.45 Pa). The explanation is that after stenting in the MV, the flow was redistributed immediately after percutaneous coronary intervention (PCI) and reversed back to its original 8 months later. However, the growth of the fibrous tissue causing in‐stent restenosis (ISR) is prohibited by sirolimus on the stent struts. In contrast, in a branch opened up by plain old balloon angioplasty (POBA), the flow did not change much, the flow could even be worse because it is shifted to the MV after the cross‐sectional area of the MV improved by stenting. However, thanks to POBA, there is increased fibrous tissue formation, enough to increase the SS and prevent further accumulation of cell and cholesterol needed for more restenosis. Conclusion: In the provisional approach, low endothelial SS correlated with no restenosis for patients who underwent stenting of the MV, while a contradictory combination of high SS and no restenosis was seen in the SB after only POBA. The mechanism of prevention of restenosis in the SB is by increasing the SS while in the MV, the mechanism of prevention of ISR is secondary to sirolimus on the stents struts. (J Interven Cardiol 2010;23:319–329)     

Transmural Mapping of Myocardial Refractoriness and Endocardial Dispersion of Repolarization in an Ovine Model of Chronic Myocardial Infarction

Background: Myocardial refractoriness and repolarization is an important electrophysiological property that, when altered, increases the risk of arrhythmogenesis. These electrophysiological changes associated with chronic myocardial infarction (MI) have not been studied in detail. We assessed the influence of left ventricular (LV) scarring on local refractoriness, repolarization, and electrogram characteristics. Methods: MI was induced in five sheep by percutaneous left anterior descending artery occlusion for 3 hours. Mapping was performed at 19 ± 6 weeks post‐MI. A total of 20 quadripolar transmural needles were deployed at thoracotomy in the LV within and surrounding scar. Bipolar pacing was performed from each needle to assess the effective refractory period (ERP) of the subendocardium and subepicardium. The activation (AT) and repolarization (RT) times, and modified activation recovery interval (ARI_m) were determined from endocardial unipolar electrograms recorded in sinus rhythm simultaneously from all needles. Scarring was quantified histologically and compared with electrophysiological characteristics. Results: Increased scarring corresponded with increased ERP (P < 0.01), decreased subendocardial electrogram amplitude (P < 0.001), and slope (P < 0.001). ERP did not differ between endocardium and epicardium (P > 0.05). The ARI_m and RT were prolonged during early myocardial activation (P < 0.001). After adjusting for AT, the RT and ARI_m were prolonged in areas of scarring (P < 0.001). After adjusting for electrogram amplitude, the ARI_m was prolonged in dense scar (P < 0.05). Conclusions: We confirmed histologically that scarring contributes to prolongation of repolarization, increased refractoriness, and reductions in conduction and voltage post‐MI. Prolongation of repolarization may be further augmented when local activation is earliest or electrogram voltage is decreased within scar.     

Sedation for Electrophysiological Procedures

Administration of intravenous sedation (IVS) has become an integral component of procedural cardiac electrophysiology. IVS is employed in diagnostic and ablation procedures for transcutaneous treatment of cardiac arrhythmias, electrical cardioversion of arrhythmias, and the insertion of implantable electronic devices including pacemakers, defibrillators, and loop recorders. Sedation is frequently performed by nursing staff under the supervision of the proceduralist and in the absence of specialist anesthesiologists. The sedation requirements vary depending on the nature of the procedure. A wide range of sedation techniques have been reported with sedation from the near fully conscious to levels approaching that of general anesthesia. This review examines the methods employed and outcomes associated with reported sedation techniques. There is a large experience with the combination of benzodiazepines and narcotics. These drugs have a broad therapeutic range and the advantage of readily available reversal agents. More recently, the use of propofol without serious adverse events has been reported. The results provide a guide regarding the expected outcomes of these approaches. The complication rate and need for emergency assistance is low in reported series where sedation is administered by nonspecialist anesthesiology staff.     

Impact of Interatrial Septum Anatomic Features on Short‐ and Long‐Term Outcomes After Transcatheter Closure of Patent Foramen Ovale: Single Device Type Versus Anatomic‐Driven Device Selection Strategy

Backgrounds

We reported the short‐ and long‐term results of our institutional single center registry Interatrial Septum Interventions Study (ISIS) about the impact of different anatomic characteristics and related device selection in patent foramen ovale (PFO) closure.

Methods

Over a 9 year period (September 2003–September 2012) we prospectively enrolled 340 consecutive patients (mean age 44 ± 15. 5 years, 198 females) who had been referred to our center for PFO catheter‐based closure. The first 105 patients received a single type of device independently from the anatomy (single device strategy). The remaining 235 patients received a different device based on intracardiac echocardiographic study of interatrial septum anatomy (anatomic strategy).

Results

Immediate success rate was 100% in both groups, whereas the rate of immediate complications was 10.4% and 2.5% (P < 0.01) in the single strategy group and anatomic strategy group, respectively. During a mean follow‐up of 59.3 ± 28.9 months, the occlusion rate was 86.6% and 94%, whereas the incidence of recurrences was 1.8% and 0% in the single device strategy group and anatomic strategy group, respectively.

Conclusion

The results from ISIS registry showed that anatomy of interatrial septum associated with PFO is quite complex leading to an increased rate of complications and a slightly lower closure rate if treated with a single device strategy.

     

Bipolar Ablation of the Interventricular Septum is More Efficient at Creating a Transmural Line than Sequential Unipolar Ablation

Introduction: Post infarct ventricular tachycardia (VT) often involves the interventricular septum (IVS) and requires transmural septal ablation. The purpose of this study was to compare the efficacy of bipolar ablation (BIA) versus sequential unipolar ablation (SUA) in creating a transmural ablation line along the IVS scar border.
Methods and Results: Both ablation strategies were compared in a phantom agar model first and then in 10 post infarct sheep. In the phantom agar model BIA lesions were larger, transmural, and less dependent on catheter alignment and contact compared with SUA. Noncontact mapping was used in the animals to identify the septal scar border and create a 30-mm ablation line. In five animals BIA (50 W) was performed between two irrigated catheters on either side of the IVS, and in five control animals SUA (50 W) was performed, first on the left ventricle (LV) septal scar border and then on the opposing right ventricle (RV) septal surface. Electrical block along ablation lines was confirmed with noncontact mapping. BIA required significantly less ablations (12 ± 1 vs 29 ± 7, P = 0.001), ablation time (22 ± 3 vs 48 ± 6 minutes, P < 0.001), and energy (58 ± 7 vs 124 ± 21 kJ, P < 0.001). At pathological examination all ablation lines in both groups were transmural at the IVS border. BIA endocardial ablation lines (LV + RV) were significantly longer than SUA lines (76 ± 10 vs 49 ± 11 mm, P = 0.003).
Conclusion: BIA of the IVS is highly effective at creating a transmural ablation line, requiring less ablation and creating longer lesions than SUA. BIA ablation may have a role for post infarct VT involving the IVS. (PACE 2010; 33:16–26)     

Left Atrial Dysfunction in Patients with Patent Foramen Ovale and Atrial Septal Aneurysm Scheduled for Transcathter Closure May Play a Role in Aura Genesis

Background: It has been suggested that a left atrial (LA) dysfunction induced by large shunt and large atrial septal aneurysm (ASA) may act as a concurrent mechanism of arterial embolism in patients with patent foramen ovale (PFO) and prior stroke. We aimed to evaluate the potential contribution of this mechanism as trigger of migraine in patients with PFO. Methods: From January 2007 to September 2009, we prospectively enrolled subjects with migraine who underwent percutaneous PFO closure. Echocardiographic parameter of LA dysfunction was evaluated: pre‐ and postoperative values were compared to values of different sex and heart rate matched populations: 30 healthy patients, 21 migraine patients without PFO (MwoPFO), and a group of 25 PFO patients without migraine (PFOwoM). The Migraine Disability Assessment Score (MIDAS) was used to assess the incidence and severity of migraine. Results: Forty‐five patients (38 females, mean age 38 ± 6.7 years, mean MIDAS 35.8 ± 4.7, and 28 patients with migraine with aura) fulfilled the inclusion criteria. After successful percutaneous closure (mean follow‐up of 18.2 ± 4.8 months), PFO closure remained complete in 95%; 35 of 45 patients reported resolution or amelioration of migraine (mean MIDAS score 12.3 ± 8.8, P < 0.03). All patients with aura reported aura resolution. Preclosure values demonstrated significantly greater LA dysfunction, when compared with healthy and MwoPFO groups. Among patients in the study group, only patients with migraine with aura showed LA dysfunction comparable to PFOwoM patients. Conclusion: This study suggests that LA dysfunction probably does not contribute to migraine itself but may play a role in the genesis of aura symptoms. (J Interven Cardiol 2010;23:370–376)     

Editorial: At the Bifurcation of the Last Frontiers

The concept of coronary angioplasty percutaneous coronary intervention (PCI) was pioneered by Andreas Gruntzig. Since then, several modifications, innovative devices, techniques, and advances have revolutionized the practice of interventional cardiology. Coronary bifurcation and chronic total occlusion are the last two frontiers that continue to challenge the skills of the interventional cardiologists. Proceedings of the second Bifurcation Summit held from November 26 to 28, 2009 in Nanjing, China are published in this symposium. In a general review, the state of the art in management of bifurcation lesion is summarized in the statement of the “Bifurcation Club in KOKURA.” A new‐presented concept was the “extension distance” between the main vessel and the sidebranch ostia and its association with restenosis. The results of two studies on shear stress (SS) after PCI showed that contradictory lower SS after stenting was associated with lower in‐stent restenosis. There was better fractional flow reserve after double kissing crush technique than provisional one‐stent technique. There was also lower rate of stent thrombosis after bifurcation stenting with excellent final angiographic results. In a negative note, the SYNTAX score had no predictive values on trifurcated left main stenting. In summary, different aspects of percutaneous management for bifurcated lesion are described seen from different perspectives and evidenced by novel techniques and strategies. (J Interven Cardiol 2010;23:293–294)