BACKGROUND:Variants in the KCNQ1 underlie type 1 long QT syndrome. The clinical manifestations are influenced by the specific KCNQ1 pathogenic variant. OBJECTIVE:We aimed to describe the phenotype in patients found to possess the p.Gln530Ter-KCNQ1 pathogenic variant common in Scandinavian patients with long QT syndrome. METHODS:Clinical characteristics of p.Gln530Ter-KCNQ1 variant-positive patients from 6 university hospital registries in Sweden, Denmark, Norway, and the United States were compared with carriers of other KCNQ1 pathogenic variants (non-p.Gln530Ter-KCNQ1) and gene-negative controls. Cardiac events (CEs) encompassed syncope of unknown origin and ventricular arrhythmias (VAs) (episodes of torsades de pointes, appropriate implantable cardioverter-defibrillator shocks, aborted cardiac arrest, or sudden cardiac death). RESULTS:The p.Gln530Ter-KCNQ1, non-p.Gln530Ter-KCNQ1, and control groups included 139 (65% female; 24% probands; mean age at end of follow-up 51 ± 20 years), 194 (65% female; mean age 44 ± 19), and 717 individuals (55% female; mean age 39 ± 24), respectively. CEs by 60 years of age were reported in 30 of the p.Gln530Ter-KCNQ1 group (22%; of those 5 VA, all nonfatal), 46 of the non-p.Gln530Ter-KCNQ1 group (24%; 4 VA, all nonfatal), and 81 of controls (11%; no VA). In the p.Gln530Ter-KCNQ1 group, CE occurred at a significantly older age than in the non-p.Gln530Ter-KCNQ1 group (44 ± 22 vs 31 ± 22; P = .02). Before 30 years of age, CE risk in the p.Gln530Ter-KCNQ1 group did not differ from that in controls (adjusted hazard ratio 1.11 [95% confidence interval 0.65-1.89]; P = .707) and was significantly lower than in the non-p.Gln530Ter-KCNQ1 group. After 30 years of age, CE risk in the p.Gln530Ter-KCNQ1 group increased significantly (adjusted hazard ratio 3.21 [95% confidence interval 1.49-6.92]; P = .003, compared with controls) and did not differ from the non-p.Gln530Ter-KCNQ1 group. CONCLUSION:The p.Gln530Ter-KCNQ1 variant is associated with a later onset of CE than other KCNQ1 pathogenic variants.

Aims:The number of patients undergoing catheter ablation is continuously growing, and techniques are improving. However, studies reporting contemporary data on catheter ablations from large real-world populations are scarce. This study aims to report characteristics and outcomes of catheter ablation from 2006 to 2020, using a nationwide registry with virtually complete coverage. Methods and results:From the Swedish Catheter Ablation Registry, patients >18 years of age undergoing catheter ablation from 2006 to 2020 were included. Periprocedural data and baseline characteristics were recorded retrospectively. A total of 61 243 procedures were included. There was an overall increase in the number of catheter ablations performed. From 2006, the number of atrial fibrillation (AF) ablations performed increased from 352 procedures in 2006 to 2609 procedures in 2020. Decreased procedural times were seen in catheter ablation of accessory pathway/Wolff-Parkinson-White syndrome, atrial tachycardia (AT), atrioventricular nodal reentry tachycardia, cavotricuspid isthmus (CTI), AF, and atrioventricular junction. Between the time periods 2006-15 and 2016-20, median procedural time in AF ablations decreased from 180 to 140 min (P < 0.001). There was a decreased trend in fluoroscopy time and median dose area product for all ablation procedures (P < 0.001). For AT, CTI, and AF, the cumulative probability of requiring a repeat ablation was significantly lower for procedures performed after January 2016 (P < 0.001). Conclusion:With a yearly increase in the number of ablations performed, there was a reduction in the need for repeat ablations for AF, AT, and CTI, along with reduced procedural times and lower fluoroscopy levels.

Abstract Background Despite the utilization of 3D-mapping systems, the use of fluoroscopy is still necessary in most procedures of catheter ablations of arrhythmias, but associated with serious health risks to both patients and operators. However, given the rapid improvement of the 3D-mapping systems, the usage of fluoroscopy has likely decreased during the past 15 years. Purpose The purpose of this study was to explore trends over time in usage of fluoroscopy in catheter ablation for all arrhythmias. Methods The Swedish Catheter Ablation Registry covers virtually all (>97%) catheter ablations performed in Sweden since 2005. Patients >18 years of age undergoing catheter ablation from January 1st 2006 to December 31st 2020 were included. Periprocedural data; median dose area product and fluoroscopy time were analyzed and compared. Periprocedural data were compared between 2006, 2015 and 2020 to find possible trends. Results A total of 61242 procedures were performed during the study period. The breakdown between the different arrhythmias was: 3% ventricular tachycardia (VT), 3% premature ventricular complex (PVC), 5% atrial tachycardia (AT), 7% atrioventricular junction ablation (AVJ), 10% atrioventricular reentry tachycardia (AVRT), 14% cavotricuspid isthmus ablation (CTI), 20% atrioventricular nodal reentry tachycardia (AVNRT) and 39% atrial fibrillation (AF). In 2006, the median fluoroscopy duration for AF, VT and PVC were recorded at 41, 32 and 37 minutes, respectively. Subsequently in 2015 the corresponding times were recorded at 14, 8 and 13 minutes. In 2020 respective procedures had a median fluoroscopy time of 11, 10 and 18 minutes (p< 0.001 for trend for all ablations). In 2006 median dose area product for AF, VT and PVC were 3998 cGycm2, 4300 cGycm2, and 5138 cGycm2, respectively. By 2015 the median dose area product had decreased to 1005 cGycm2, 432 cGycm2 and 1123 cGycm2 respectively. In 2020 the median dose area product had decreased further to 524 cGycm2, 380 cGycm2 and 848 cGycm2 (p<0.001 for trends for all ablations). See figure 1 for all procedures. Conclusion Fluoroscopy time and median dose area product have decreased significantly over a 15-year period and have stabilized on a low level over the last 5 years. Given the associated risks, efforts to further reduce radiation exposure are clearly warranted.Median dose area product

Abstract Background The number of patients undergoing catheter ablation of atrial fibrillation (AF) is continuously growing, and techniques are improving. However, AF recurrences are still common and demand frequent redo procedures that expose patients to repeat complication risks and cause extensive health care costs. Real-life data regarding redo rates is scarce. Using a national registry, we examined current trends in long-term outcomes as illustrated by the need for redo procedures. Purpose The purpose of this study was to investigate the long-term outcome of catheter ablation of AF as a function of when the initial procedure was performed. Methods The Swedish Catheter Ablation Registry covers virtually all (>97%) catheter ablations performed in Sweden since 2005. Patients >18 years of age undergoing pulmonary vein isolation (PVI) during January 1st 2006 until December 31st 2020 were included in the analysis. Follow up data was registered until December 31st 2021. The number of procedures performed, characteristics of patients, acute success (defined as all pulmonary veins isolated), and repeat ablation at 1 and 3 years were analyzed. Characteristics and periprocedural data were compared between 2006, 2015 and 2020 to find possible trends. Results A total of 23909 PVI were performed during the studied period. In 2006, 2015 and 2020, respectively, 352, 1861 and 2609 procedures were performed, constituting 18%, 40% and 48% of all ablation procedures. There was an increase in patient age (58, 62, 64 years) and more women were ablated (22%, 27%, 28%) over time. Acute success rate remained high at 98% during the study period. Repeat ablation at 1 and 3 years was 23% and 45% respectively for patients ablated in 2006, compared to 14% and 30% in 2015, and 10% and 23% in 2018 (p <0.001 for both trends), see figure 1. Conclusion In a setting of a universal healthcare system, with a continuous increase in amount of catheter ablation of AF, in spite of an unchanged, high acute success throughout the study period, a continuous decrease of repeat ablation was observed indicating a substantial gain in patient value by AF ablation over time.Repeat ablation atrial fibrillation

Abstract Background Patients carrying genetic variants associated with long QT syndrome (LQTS) who initially present with normal QTc (concealed LQTS) is a large and growing group of patients. Long-term progression of QTc interval and risk factors associated with arrhythmic events in this patient group remain poorly described. Purpose 1) To assess the prevalence of concealed LQTS among patients with genetically verified LQTS; 2) To explore genetic factors associated with QTc prolongation and arrhythmic events in patients with concealed LQTS. Methods Adult LQTS patients (LQT1-3) from three cardiogenetic clinics in Sweden were included in a prospective register. Digital ECGs recorded for any reason both in-hospital and in outpatient settings, were retrieved from ECG archives. Concealed LQTS was defined as QTcB < 460 ms in men or <470 ms in women at initial presentation. The proportion of patients exhibiting QTcB above 480, 490 and 500 ms thresholds at any time during follow-up (FU) was assessed. Ventricular arrhythmias (VA) were defined as torsades de pointes, appropriate ICD shock, aborted cardiac arrest or sudden cardiac death. Cardiac events (CE) were defined as VA or syncope. The risk of CE and VA by the age of 60 years associated with LQTS genotype, KCNH2 pore region mutations and KCNQ1 membrane-spanning mutations was assessed using Kaplan Meier survival curve analysis and Cox regression analysis adjusted for sex, proband status and beta blocker use. Results 1). Out of 211 LQTS patients, 89 (42%) had concealed LQTS (52 (58%) women, 22 (25%) probands, 16 (18%) had CE by the time of diagnosis). Median age at diagnosis was 39 [IQR 22-55] years, age at the end of FU 47 [31-62] years. Concealed LQTS prevalence did not differ between genotypes: LQT1 – 59/141 (42%), LQT2 – 25/57 (44%), LQT3 – 5/13 (39%). 2). LQT1 patients were least and LQT3 patients were most prone to develop QTc prolongation during FU (Table). 3). VA were reported in 3 (3.5%) patients and in all cases preceded by syncope. None of the LQT1 patients experienced VA during FU. Both VA events among LQT2 patients were reported in carriers of KCNH2 pore region mutations (log rank p=0.023). 4). Patients with LQT2 were at higher risk to develop CE than LQT1 patients (HRadj=3.04 95%CI 1.22-7.55). Among LQT1 patients, carriers of mutations affecting membrane-spanning KCNQ1 channel region tended to have higher risk of CE (log rank p=0.018, HRadj=3.99 95%CI 0.80-19.89). Conclusions Concealed LQTS patients represent a significant proportion of the LQTS population and are similarly distributed between the most common LQTS genotypes. These patients have low risk of VA, which is confined to LQT3 patients and LQT2 patients carrying KCNH2 pore region mutations. Concealed LQT1 patients are at the lowest risk of CE and VA and have the lowest risk of experiencing QTc prolongation during FU. Carriers of mutations affecting KCNQ1 membrane-spanning region represent the high-risk LQT1 group with regard to CE.Concealed LQTS patients characteristicsRisk of VA in concealed LQTS by genotype

Background Dormant coronary collaterals are highly prevalent and clinically beneficial in cases of coronary occlusion. However, the magnitude of myocardial perfusion provided by immediate coronary collateral recruitment during acute occlusion is unknown. We aimed to quantify collateral myocardial perfusion during balloon occlusion in patients with coronary artery disease (CAD). Methods Patients without angiographically visible collaterals undergoing elective percutaneous transluminal coronary angioplasty (PTCA) to a single epicardial vessel underwent two scans with 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). All subjects underwent at least three minutes of angiographically verified complete balloon occlusion, at which time an intravenous injection of the radiotracer was administered, followed by SPECT imaging. A second radiotracer injection followed by SPECT imaging was performed 24 h after PTCA. Results The study included 22 patients (median [interquartile range] age 68 [54-72] years. The perfusion defect extent was 19 [11-38] % of the LV, and the collateral perfusion at rest was 64 [58-67]% of normal. Conclusion This is the first study to describe the magnitude of short-term changes in coronary microvascular collateral perfusion in patients with CAD. On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provided more than half of the normal perfusion.

AIMS:To investigate the association of iatrogenic cardiac tamponades as a complication of invasive electrophysiology procedures (EPs) and mortality as well as serious cardiovascular events in a nationwide patient cohort during long-term follow-up. METHODS:From the Swedish Catheter Ablation Registry between 2005 and 2019, a total of 58 770 invasive EPs in 44 497 patients were analysed. From this, all patients with periprocedural cardiac tamponades related to invasive EPs were identified (n = 200; tamponade group) and matched (1:2 ratio) to a control group (n = 400). Over a follow-up of 5 years, the composite primary endpoint-death from any cause, acute myocardial infarction, transitory ischaemic attack (TIA)/stroke, and hospitalization for heart failure-revealed no statistically significant association with cardiac tamponade [hazard ratio (HR) 1.22 (95% CI, 0.79-1.88)]. All single components of the primary endpoint as well as cardiovascular death revealed no statistically significant association with cardiac tamponade. Cardiac tamponade was associated with a significantly higher risk with hospitalization for pericarditis [HR 20.67 (95% CI, 6.32-67.60)]. CONCLUSION:In this nationwide cohort of patients undergoing invasive EPs, iatrogenic cardiac tamponade was associated with an increased risk of hospitalization for pericarditis during the first months after the index procedure. In the long-term, however, cardiac tamponade revealed no significant association with mortality or other serious cardiovascular events.

Background: There is sufficient collateral flow to prevent myocardial ischemia during balloon occlusion in approximately one in five patients. However, the magnitude of myocardial perfusion provided by the coronary collateral circulation during occlusion is unknown. Therefore, the aim of this study was to quantify collateral myocardial perfusion during balloon occlusion in patients with coronary artery disease (CAD). Methods: Patients without angiographically visible collaterals undergoing elective percutaneous transluminal coronary angioplasty (PTCA) to a single epicardial vessel underwent two scans with 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). All subjects underwent at least three minutes of angiographically verified complete balloon occlusion, at which time an intravenous injection of the radiotracer was administered, followed by SPECT imaging. A second radiotracer injection followed by SPECT imaging was performed 24 hours after PTCA. Results: The study included 21 patients (median [interquartile range] age 70 [56-74] years, 48% female). The diameter stenosis ranged from 60-99%, with successful PTCA performed with a mean 5-minute balloon occlusion. The perfusion defect extent was 16 [8-30]% of the LV. The collateral perfusion at rest was 64 [58-68]% of normal perfusion. Collateral perfusion was negatively correlated with perfusion defect size (R2=0.85, p<0.001), and did not differ by sex (p=0.27) or age (p=0.58). Conclusions: This is the first study to describe the magnitude of coronary microvascular collateral perfusion in patients with CAD. On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provide approximately 60% of the perfusion that reaches the jeopardized myocardium during coronary occlusion.

Abstract Funding Acknowledgements Type of funding sources: None. BACKGROUND The coronary collateral circulation is a preformed network of anastomotic connections acting as a "natural bypass" mechanism. Whilst the prevalence of collaterals varies between species, approximately 25% of patients have angiographically visible robust collaterals at the time of ST elevation myocardial infarction. While the presence of collaterals is associated with improved outcomes, the magnitude of myocardial perfusion which can be provided by the collateral circulation remains uncertain. PURPOSE The aim was to quantify collateral myocardial perfusion during experimental coronary balloon occlusion in patients with CAD. METHODS The study was approved by the local investigational review board, and all patients provided informed consent. Patients without prior infarction, bypass surgery, or angiographically visible collaterals undergoing elective percutaneous transluminal coronary angioplasty (PTCA) to a single epicardial vessel, underwent two scans with 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). All subjects underwent at least three minutes of angiographically verified complete balloon occlusion, at which time an intravenous injection of the radiotracer was administered, followed by SPECT imaging. A second radiotracer injection followed by SPECT imaging was performed 24 hours after PTCA. RESULTS The study included 21 patients (median [interquartile range] age 70 [56-74] years, 52% male). The degree of diameter stenosis of treated vessels ranged from 60-99%, with successful PTCA performed with a mean 5-minute balloon occlusion time, resulting in ≤20% residual stenosis in all cases. The vessels undergoing PTCA were 6 in the LAD, 5 in the LCx, and 10 in the RCA. For the cohort, the size of the perfusion defect was 16 [8-30]% of the LV and the collateral perfusion at rest within the perfusion defect was 64 [58-68]% of normal perfusion within that region. Collateral perfusion was negatively correlated with perfusion defect size (R2 = 0.85, p < 0.001), but did not differ by sex (p = 0.27) or age (p = 0.58). CONCLUSIONS: This is the first study to describe the magnitude of microvascular collateral perfusion in CAD. On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provide approximately 60% of the perfusion that reaches the jeopardized myocardium during coronary occlusion. This magnitude of collateral perfusion is much higher than previously speculated. A previous study using microspheres in dogs found that collateral perfusion in the setting of an occluded vessel was 6% of normal. By comparison, the current study found ten times greater collateral perfusion in patients with CAD. Abstract Figure. Collateral perfusion during occlusion.

Aims Catheter ablation is considered the treatment of choice for many tachyarrhythmias, but convincing real-world' data on efficacy and safety are lacking. Using Swedish national registry data, the ablation spectrum, procedural characteristics, as well as ablation efficacy and reported adverse events are reported. Methods and Results Consecutive patients (18years of age) undergoing catheter ablation in Sweden between 01 January 2006 and 31 December 2015 were included in the study. Follow-up (repeat ablation and vital status) was collected through 31 December 2016. A total of 26642 patients (5715years, 62% men), undergoing a total of 34428 ablation procedures were included in the study. In total, 4034 accessory pathway/Wolff-Parkinson-White syndrome (12%), 7358 AV-nodal re-entrant tachycardia (21%), 1813 atrial tachycardia (5.2%), 5481 typical atrial flutter (16%), 11916 atrial fibrillation (AF, 35%), 2415 AV-nodal (7.0%), 581 premature ventricular contraction (PVC, 1.7%), and 964 ventricular tachycardia (VT) ablations (2.8%) were performed. Median follow-up time was 4.7years (interquartile range 2.7-7.0). The spectrum of treated arrhythmias changed over time, with a gradual increase in AF, VT, and PVC ablation (P<0.001). Decreasing procedural times and utilization of fluoroscopy with time, were seen for all arrhythmia types. The rates of repeat ablation differed between ablation types, with the highest repeat ablation seen in AF (41% within 3years). The rate of reported adverse events was low (n=595, 1.7%). Death in the immediate period following ablation was rare (n=116, 0.34%). Conclusion Catheter ablations have shifted towards more complex procedures over the past decade. Fluoroscopy time has markedly decreased and the efficacy of catheter ablation seems to improve for AF.

Background: Catheter ablation has become the treatment of choice for many tachyarrhythmias. The ablation techniques are continuously refined and the indications expanded, enabling treatment of more ...

Patients with acute coronary occlusion (ACO) may not only have ischemia‐related ST‐segment changes but also changes in the QRS complex. It has recently been shown in dogs that a greater ischemic QRS prolongation (IQP) during ACO is related to lower collateral flow. This suggests that greater IQP could indicate more severe ischemia and thereby more rapid infarct development. Therefore, the purpose was to evaluate the relationship between IQP and measures of myocardial injury in patients presenting with acute ST‐elevation myocardial infarction (STEMI).

Objectives. An acute coronary occlusion and its possible subsequent complications is one of the most common causes of death. One such complication is ventricular fibrillation (VF) due to myocardial ischemia. The severity of ischemia is related to the amount of coronary arterial collateral flow. In dog studies collateral flow has also been shown to be associated with QRS prolongation. The aim of this study was to investigate whether ischemic QRS prolongation (IQP) is associated with impending VF in an experimental acute ischemia dog model. Methods. Degree of IQP and occurrence of VF were measured in dogs (n=21) during coronary occlusion for 15min and also during subsequent reperfusion (experiments conducted in 1984). Results. There was a significant difference in absolute IQP between dogs which developed VF during reperfusion (47 +/- 29ms, mean +/- SD) and those which did not (12 +/- 10ms; p=.001). Conclusions. IQP during acute coronary occlusion is associated with reperfusion VF in an experimental dog model and might therefore be a potential predictor of malignant arrhythmias in patients with acute coronary syndrome.