The Current Landscape of Ventricular Tachycardia Trials: A Systematic Review of Registered Studies.

BACKGROUND: Although there are evolving techniques and technologies for treating ventricular tachycardia (VT), the current landscape of clinical trials for managing VT remains understudied. OBJECTIVE: The objective of this study was to provide a systematic characterisation of the interventional management of VT through an analysis of the ClinicalTrials.gov, clinicaltrialsregister.eu, anzctr.org.au and chictr.org.cn databases. METHODS: We queried all phase II to IV interventional trials registered up to November 2023 that enrolled patients with VT. Published, completed but unpublished, terminated, or ongoing trials were included for final analysis. RESULTS: Of the 698 registered studies, 135 were related to VT, with 123 trials included in the final analysis. Among these trials, 25 (20%) have been published, enrolling a median of 35 patients (interquartile range [IQR] 20-132) over a median of 43 months (IQR 19-62). Out of the published trials, 14 (56%) were randomised, and 12 (48%) focused on catheter ablation. Twenty-two (18%) have been completed but remain unpublished, even after a median of 36 months (IQR 15-60). Furthermore, 27 (22%) trials were terminated or withdrawn, with the most common cause being poor enrolment. Currently, 49 (40%) trials are ongoing and novel non-ablative technologies, such as radioablation and autonomic modulation, account for 35% and 8% of ongoing trials, respectively. CONCLUSIONS: Our analysis revealed that many registered trials remain unpublished or incomplete, and randomised controlled trial evidence is limited to only a few studies. Furthermore, many ongoing trials are focused on non-catheter ablation-based strategies. Therefore, larger pragmatic trials are needed to create stronger evidence in the future.

Correlation of spatial patterns of endocardial pace mapping to underlying scar topography in patients with scar-related ventricular tachycardia.

INTRODUCTION: Endocardial pace mapping (PM) can identify conducting channels for ventricular tachycardia (VT) circuits in patients with structural heart disease (SHD). Recent findings show the temporal and spatial pattern of PM may aid identification of the surface harboring VT isthmii. The specific correlation of PM patterns to scar topography has not been examined. OBJECTIVE: To correlate the pattern of endocardial PMs to underlying scar topography in SHD patients with VT. METHODS: Data from patients undergoing VT ablation from August 2018 to February 2022 were reviewed. RESULTS: Sixty-three patients with SHD-related VT (mean age 65 ± 14 years) with 83 endocardial PM correlation maps were analysed. Two main correlation patterns were identified, an "abrupt-change correlation pattern (AC-pattern)" and "centrifugal-attenuation correlation pattern (CA-pattern)." AC-pattern had lower scar ratio (unipolar/bipolar % scar area; 1.1 vs. 1.5, p < .001), had longer maximal stimulus-QRS intervals (97.5 vs. 68 ms, p = .002), and higher likelihood of endocardial dominant scar (11/21 [52%] vs. 3/38 [8%], p < .001) than CA-pattern seen on intracardiac echocardiography (ICE). In contrast, CA-pattern was more likely to have epicardial dominant scar or mid-intramural scar on ICE (epicardial dominant scar; CA-pattern: 12/38 [32%] vs. AC-pattern: 1/21 [5%], p = .02, mid-intramural scar; CA-pattern: 15/38 [39%] vs. AC-pattern: 1/21 [5%], p = .005). CONCLUSIONS: The spatial pattern of endocardial PM in SHD-related VT directly correlates with scar topography. AC-pattern is associated with endocardial dominant scar on ICE with lower scar ratio and longer stimulus-QRS intervals, whereas CA-pattern is strongly associated with epicardial dominant or mid-intramural scar with higher scar ratio and shorter stimulus-QRS intervals.

Contemporary updates on ventricular arrhythmias: from mechanisms to management.

Ventricular arrhythmias (VAs) are a group of heart rhythm disorders that can be life-threatening and cause significant morbidity. VA in the presence of structural heart disease (SHD) has distinct prognostic implications and requires a comprehensive and multifaceted approach for investigation and management. Early specialist referral should be considered for all patients with VA. Particular urgency is recommended in patients with syncope, nonsustained/sustained VA on Holter monitor and SHD on cardiac imaging because of the heightened risk of sudden cardiac death. Comprehensive phenotyping is recommended for most patients with VA, encompassing noninvasive cardiac functional testing, multimodality imaging and genetic testing in select circumstances. Management of idiopathic VA is guided heavily by symptom burden and the presence of ventricular systolic impairment. In SHD, guideline-directed heart failure therapy and device implantation are critical considerations. Whilst commonly used and well-established, antiarrhythmic drugs can be hampered by toxicity and failure of adequate arrhythmia control. Catheter ablation is increasingly being considered a feasible first-line alternative to medical therapy, where outcomes are influenced by disease aetiology and scar burden in SHD. Catheter ablation is associated with reduced arrhythmia recurrence and burden and improved quality of life at follow-up.

Electrophysiologic and electroanatomic characterization of ventricular arrhythmias in non-compaction cardiomyopathy: A systematic review.

BACKGROUND: Non-compaction cardiomyopathy (NCCM) is a form of structural heart disease prone to ventricular arrhythmias (VAs) and sudden cardiac death. Non-compacted myocardium may harbor VA substrate, though some reports suggest otherwise. OBJECTIVE: This study aimed to characterize the electrophysiologic (EP) features of VA in NCCM. METHODS: We performed a systematic review of case reports, case series, and observational studies. RESULTS: One hundred and thirty-five cases of NCCM from studies between 2000 and 2020 were included. Mean age was 34 ± 20 years, mean left ventricular (LV) ejection fraction was 42 ± 15% with two cases having late gadolinium enhancement on magnetic resonance imaging. The LV apex was the most common non-compacted segment (86%); 10% involved the right ventricle (RV). Antiarrhythmic failure was documented in 16 cases, of which 50% failed more than one agent. Only 23% of monomorphic VAs localized to regions of non-compaction on electrocardiogram. Most frequently, VAs localized to the RV outflow tract (n = 21), posterior fascicle (n = 19), and anterolateral LV apex (n = 9). All cases with apical exits arose from the non-compacted myocardium. On EPS, 83% of sustained VTs were due to re-entry, 17% due to focal mechanism. Catheter ablation was performed in 39 cases, with 7 requiring more than 1 procedure. Acute VA non-inducibility was achieved in 82% and VA-free survival was reported in 85% over a mean follow-up of 24 months. CONCLUSION: The majority of VAs in NCCM arise remotely from non-compacted myocardium, and non-re-entrant mechanism seen in ~1/5th of sustained VTs. Catheter ablation outcomes appear favorable. Further study is needed to understand the pathophysiology of VA in NCCM.

Prognostic significance of extensive versus limited induction protocol during catheter ablation of scar-related ventricular tachycardia.

INTRODUCTION: Testing for inducible ventricular tachycardia (VT) pre- and postablation forms the cornerstone of contemporary scar-related VT ablation procedures. There is significant heterogeneity in reported VT induction protocols. We examined the utility of an extensive induction protocol (up to 4 extra-stimuli [ES] ± burst ventricular pacing) compared to the current guideline-recommended protocol (up to 3ES, defined as limited induction protocol) in patients with scar-related VT. METHODS AND RESULTS: Sixty-two patients (age: 64 ± 14 years; left ventricular ejection fraction: 37 ± 13%, ischemic cardiomyopathy: 31, nonischemic cardiomyopathy: 31) with at least one inducible VT were included. An extensive testing protocol induced 11%-17% more VTs, compared to the limited induction protocol before, and after the final ablation. VT recurred in 48% of patients during a mean follow up of 566 ± 428 days. Patients who were noninducible for any VT using the limited induction protocol had worse ventricular arrhythmia (VA)-free survival (12 months, 43% vs. 82%; p = .03) and worse survival free of VA, transplantation and mortality (12 months 46% vs. 82%; p = .02), compared to patients who were noninducible for any VT using the extensive induction protocol. CONCLUSIONS: Between 11% and 17% of inducible VTs may be missed if 4ES and burst pacing are not performed in induction protocols before and after ablation. Noninducibility for any VT after an extensive induction protocol after the final ablation portends more favorable prognostic outcomes when compared with the current guideline-recommended induction protocol of up to 3ES. This data suggests that the adoption of an extensive induction protocol is of prognostic benefit after VT ablation.

The role of multimodality imaging in the diagnosis of left ventricular noncompaction.

Left ventricular noncompaction (LVNC) is a heterogeneous entity and, in reality, a likely spectrum of disease which is clinically associated with arrhythmia, thromboembolic complications and sudden cardiac death. With the emergence of cardiac MRI (cMRI), the phenotype is increasingly more prevalent, resulting in clinical uncertainty regarding prognosis and management. The currently accepted hypothesis suggests an early embryonic arrest of the normal, sequential myocardial compaction process. LVNC is observed in isolation or in association with congenital heart disease, neuromuscular disease or a vast array of genetic cardiomyopathies. Definition of the entity varies among international society guidelines with differences both within and between imaging modalities, predominantly echocardiography and cMRI. Long-term prognostic data are emerging but due to the intrinsic variability in reported prevalence, selection bias and lack of pathological to prognostic correlation, there are many uncertainties regarding clinical management. This review seeks to clarify the role of multimodality imaging in diagnosis and management of the disease. We discuss the sensitivity and specificity of the current diagnostic criteria, as well as the nuances in diagnosis using the available imaging modalities.

Catheter Ablation of VT in Non-Ischaemic Cardiomyopathies: Endocardial, Epicardial and Intramural Approaches.

Non-ischaemic cardiomyopathy (NICM) encompasses a heterogeneous group of disorders that includes genetic, idiopathic, post viral and inflammatory cardiomyopathies. NICM is associated with an increased risk of ventricular arrhythmias (VAs), namely in the form of ventricular tachycardia (VT). Although implanted cardiac defibrillators (ICD) may prevent sudden death from VA, NICM patients may suffer from recurrent symptoms and ICD therapies, and anti-arrhythmic drug side effects. Catheter ablation is highly efficacious in NICM, however poses unique challenges when compared to post myocardial infarction substrates. NICM substrates are fundamentally different in scar location, extent, and transmurality which results in variable electrophysiologic properties and less apparent ablation targets during sinus rhythm, compared to ischaemic cardiomyopathy. NICM substrates can be intramural and/or epicardial, posing challenges to accessibility, which likely accounts for the observed higher rates of arrhythmia recurrence following ablation. Substrate location is influenced by the underlying aetiology (inflammatory, genetic), and can be gleaned from a combination of unique 12-lead electrocardiogram VT patterns, distribution of late gadolinium enhancement on cardiac magnetic resonance imaging, and electroanatomic voltage mapping. With the high proportion of intramural substrate in NICM, novel techniques have become increasingly common in recent years, including sequential, simultaneous or bipolar ablation on opposite myocardial surfaces to achieve greater lesion depth; use of half normal saline for irrigation; use of a novel retractable needle within an endocardial catheter; and transcoronary/venous ethanol ablation to target more inaccessible regions. Epicardial approaches have also been improved in recent years, with advents such as the needle-in-needle technique to reduce the risk of pericardial bleeding and phrenic nerve displacement, and hybrid surgical approaches to facilitate epicardial access in the presence of adhesions. Non-invasive cardiac radiation holds promise for the future. This state-of-the-art review will summarise the incidence, mechanism, multimodal assessment and catheter ablation-based management of VA in NICM.

Efficacy and safety of catheter ablation for Brugada syndrome: an updated systematic review.

BACKGROUND: Patients with Brugada syndrome (BrS) may experience recurrent ventricular arrhythmias (VAs). Catheter ablation is becoming an emerging paradigm for treatment of BrS. OBJECTIVE: To assess the efficacy and safety of catheter ablation in BrS in an updated systematic review. METHODS: We comprehensively searched the databases of Pubmed/Medline, EMBASE, and Cochrane Central Register of Controlled Trials from inception to 11th of August 2021. RESULTS: Fifty-six studies involving 388 patients were included. A substrate-based strategy was used in 338 cases (87%), and a strategy of targeting premature ventricular complex (PVCs)/ventricular tachycardias (VTs) that triggered ventricular fibrillation (VF) in 47 cases (12%), with combined abnormal electrogram and PVC/VT ablation in 3 cases (1%). Sodium channel blocker was frequently used to augment the arrhythmogenic substrate in 309/388 cases (80%), which included a variety of agents, of which ajmaline was most commonly used. After ablation procedure, the pooled incidence of non-inducibility of VA was 87.1% (95% confidence interval [CI], 73.4-94.3; I2 = 51%), and acute resolution of type I ECG was seen in 74.5% (95% CI [52.3-88.6]; I2 = 75%). Over a weighted mean follow up of 28 months, 7.6% (95% CI [2.1-24]; I2 = 67%) had recurrence of type I ECG either spontaneously or with drug challenge and 17.6% (95% CI [10.2-28.6]; I2 = 60%) had recurrence of VA. CONCLUSION: Catheter ablation appears to be an efficacious strategy for elimination of arrhythmias or substrate associated with BrS. Further study is needed to identify which patients stand to benefit, and optimal provocation protocol for identifying ablation targets.

Efficacy and safety of catheter ablation as first-line therapy for the management of ventricular tachycardia.

BACKGROUND: Ventricular tachycardia (VT) is associated with significantly increased morbidity and mortality. Catheter ablation (CA) in line with an implantable cardioverter-defibrillator (ICD) is highly effective in VT management; however, it is unknown if CA should be considered as first-line therapy. The aim of this study is to verify the efficacy and safety of CA as first-line therapy for the first VT presentation (as adjunctive to ICD insertion), compared to initial ICD insertion and anti-arrhythmic drug (AAD) therapy. METHODS: Data from patients with the first presentation for VT from January 2017 to January 2021 was reviewed. Patients were classified as "ablation first" vs "ICD first" groups and compared the clinical outcomes between groups. RESULTS: One hundred and eighty-four consecutive patients presented with VT; 34 underwent CA as first-line therapy prior to ICD insertion, and 150 had ICD insertion/AAD therapy as first-line. During the median follow-up of 625 days, patients who underwent CA as first-line therapy had significantly higher ventricular arrhythmia (VA)-free survival (91% vs 59%, log-rank P = 0.002) and composite of VA recurrence, cardiovascular hospitalization, transplant, and death (84% vs 54%, log-rank P = 0.01) compared to those who did not undergo CA. Multivariate analysis revealed that first-line CA was the only protective predictor of VA recurrence (hazard ratio (HR) 0.20, P = 0.003). There were 3 (9%) peri-procedural complications with no peri-procedural deaths. CONCLUSION: Real-world data supports the efficacy and safety of CA as first-line therapy at the time of the first VT hospitalization, compared to the initial ICD implant and AAD therapy.

Mortality after catheter ablation of structural heart disease related ventricular tachycardia.

BACKGROUND: There is a paucity of data describing mortality after catheter ablation of ventricular tachycardia (VT). OBJECTIVES: We describe the causes and predictors of cardiac transplant and/or mortality following catheter ablation of structural heart disease (SHD) related VT. METHODS: Over 10-years, 175 SHD patients underwent VT ablation. Clinical characteristics, and outcomes, were compared between patients undergoing transplant and/or dying and those surviving. RESULTS: During 2.8 (IQR 1.9-5.0) years follow-up, 37/175 (21%) patients underwent transplant and/or died following VT ablation. Prior to ablation, these patients were older (70.3 ± 11.1 vs. 62.1 ± 13.9 years, P = 0.001), had lower left ventricular ejection fraction ([LVEF] 30 ± 12% vs. 44 ± 14%, P < 0.001), and were more likely to have failed amiodarone (57% vs. 39%, P = 0.050), compared to those that survived. Predictors of transplant and/or mortality included LVEF≤35% (HR 4.71 [95% CI 2.18-10.18], P < 0.001), age ≥ 65 years (HR 2.18 [95% CI 1.01-4.73], P = 0.047), renal impairment (HR 3.73 [95% CI 1.80-7.74], P < 0.001), amiodarone failure (HR 2.67 [95% CI 1.27-5.63], P = 0.010) and malignancy (HR 3.09 [95% CI 1.03-9.26], P = 0.043). Ventricular arrhythmia free survival at 6-months was lower in the transplant and/or deceased, compared to non-deceased group (62% vs. 78%, P = 0.010), but was not independently associated with transplant and/or mortality. The risk score, MORTALITIES-VA, accurately predicted transplant and/or mortality (AUC: 0.872 [95% CI 0.810-0.934]). CONCLUSIONS: Cardiac transplant and/or mortality after VT ablation occurred in 21% of patients. Independent predictors included LVEF≤35%, age ≥ 65 years, renal impairment, malignancy, and amiodarone failure. The MORTALITIES-VA score may identify patients at high-risk of transplant and/or dying after VT ablation.

Intracardiac echocardiography techniques to identify ventricular arrhythmia substrate.

Intracardiac echocardiography (ICE) is increasingly used to facilitate catheter ablation of ventricular arrhythmias (VA). It allows intraprocedural recognition of myocardial substrate, optimization of catheter-tissue contact, identification of anatomical barriers to ablation, and early recognition of complications. In the era where the 3-dimensionality of substrate for VA is increasingly recognized, ICE is invaluable in identifying scar topography in the endocardial, midmyocardial, and epicardial layers. ICE assists in identifying endocavitary structures that are a common source of VA in idiopathic and structural heart disease. Furthermore, as substrate imaging of the right ventricle has not been optimized with other imaging modalities, ICE offers a unique opportunity to visualize substrate in this chamber. Real-time substrate identification can be particularly useful where there are contraindications to use of other imaging modalities or the images are obscured by artefact in the presence of cardiac device leads. In this review we provide a step-by-step guide in the techniques used to image ventricular arrhythmia substrate with ICE. We also discuss the benefits and limitations of this technique in comparison to other imaging modalities.

Catheter ablation of idiopathic outflow tract ventricular arrhythmias with low intraprocedural burden guided by pace mapping.

BACKGROUND: There are limited data comparing ablation outcomes in patients with low intraprocedural burden of ventricular arrhythmias (VA) undergoing a pace mapping (PM)-guided strategy vs those with high burden guided by standard activation mapping strategy (non-PM). OBJECTIVE: We sought to determine if catheter ablation-guided by PM of low-intraprocedural-burden idiopathic outflow tract VA would be noninferior compared to non-PM-guided ablation. METHODS: Outcomes of catheter ablation of idiopathic outflow tract VA in 22 patients with a low burden of intraprocedural VA using PM-guided ablation were compared to 44 patients with a high burden of intraprocedural VA undergoing ablation using standard techniques. RESULTS: Sixty-six patients were included (age 46.5 ± 14.8 years; 68% female, left ventricular ejection fraction 59% ± 5%). Within the PM group, 24-hour preprocedure premature ventricular complex (PVC) burden was 9.5% (interquartile range [IQR] 4%-13.8%), number of pace maps 33.6 ± 18.5, surface area of ≥95% pace map correlation 1.9 ± 1.2 cm2, with best pace map correlation 96% (IQR 92%-97%). Within the non-PM group, 24-hour preprocedure PVC burden was 13.5% (IQR 6.6%-30%), earliest activation time -33.7 ± 9.9 ms. Procedural duration, general anesthesia administration, fluoroscopy dose, and complications were all comparable. Following final procedure, 24-hour VA burden (PM 0% [IQR 0-2.4%] vs non-PM 0% [IQR 0-4.2%], P = .98), along with VA-free survival at 6-month follow-up (PM 77% vs non-PM 71%, P = .77), were both comparable. CONCLUSION: In patients with low intraprocedural burden of outflow tract VA, PM-guided catheter ablation can accurately identify the VA site of origin, leading to outcomes comparable to those achieved with standard ablation techniques.

Clinical and Electrophysiological Characteristics of Ventricular Tachycardias From the Basal Septum in Structural Heart Disease.

OBJECTIVES: This study describes the clinical and electrophysiological characteristics of basal-septal ventricular tachycardias (VTs) in patients with structural heart disease (SHD). BACKGROUND: The basal septum is a common source of VT in patients with SHD. METHODS: Data from 312 consecutive patients with SHD undergoing catheter ablation of ventricular arrhythmias were reviewed. RESULTS: Thirty-three basal-septal VTs in 31 patients (mean age 67.4 ± 14.2 years, mean left ventricular ejection fraction [LVEF] 42% ± 15%) were identified. Patients with VTs with left ventricular basal-septal breakthrough were more likely to have ischemic cardiomyopathy and lower LVEF; patients with right ventricular basal-septal VT were more likely to have sarcoidosis or right ventricular cardiomyopathy of unknown significance, with higher LVEF. Atrioventricular block was present in 45% of patients and intraventricular block including persistent biventricular pacing in 77%. Unipolar scar was larger than bipolar scar (area 18.8% ± 19.4% vs 12.7% ± 14.6%; P < 0.001). VTs with right bundle branch block configuration and S wave in lead V6 with positive V3/V4 polarity consistently indicated left ventricular basal-septal breakthrough. Inferior limb-lead discordance with right bundle branch block configuration and "reverse pattern break in lead V2" were identified in left ventricular basal inferior-septal origin in 3 patients. VT noninducibility was achieved in 55%, and VT recurred in 42% of patients after a single procedure, but VT burden was significantly reduced after ablation (59 episodes before vs 2 episodes after ablation; P = 0.02). CONCLUSIONS: Basal-septal VTs in patients with SHD have a distinct clinical, electrocardiographic, and electrophysiological profile depending on the breakthrough site, accompanied by a deep intramural septal substrate that limits procedural success after catheter ablation.

Remote magnetic navigation compared to contemporary manual techniques for the catheter ablation of ventricular arrhythmias in structural heart disease.

BACKGROUND: There are limited data comparing remote magnetic navigation (RMN) to contemporary techniques of manual-guided ventricular arrhythmia (VA) catheter ablation. OBJECTIVES: We compared acute and long-term outcomes of VA ablation guided by either RMN or contemporary manual techniques in patients with structural heart disease. METHODS: From 2010-2019, 192 consecutive patients, with ischemic cardiomyopathy (ICM) or non-ischemic cardiomyopathy (NICM) underwent catheter ablation for sustained ventricular tachycardia (VT) or premature ventricular complexes (PVCs), using either RMN (n = 60) or manual (n = 132) guided techniques. Acute success and VA-free survival were compared. RESULTS: In ICM, acute procedural success was comparable between the 2 techniques (manual 43.5% vs. RMN 29%, P = 0.11), as was VA-free survival (manual 83% vs. RMN 74%, P = 0.88), and survival free from cardiac transplantation and all-cause mortality (manual 88% vs. RMN 87%, P = 0.47), both at 12-months after final ablation. In NICM, manual compared to RMN guided, had superior acute procedural success (manual 46% vs. RMN 19%, P = 0.003) and VA-free survival 12-months after final ablation (manual 79% vs. RMN 41%, P = 0.004), but comparable survival free from cardiac transplantation and all-cause mortality 12-months after final ablation (manual 95% vs. RMN 90%, P = 0.52). Procedural duration was shorter in both subgroups undergoing manual guided ablation, whereas fluoroscopy dose and complication rates were comparable. CONCLUSION: RMN provides similar outcomes to manual ablation in patients with ICM. In NICM however, acute success, and long-term VA-free survival was better with manual ablation. Prospective, multi-centre randomised trials comparing contemporary manual and RMN systems for VA catheter ablation are needed.

Ventricular Tachycardia Ablation in Non-ischemic Cardiomyopathy.

Non-ischemic cardiomyopathies are a heterogeneous group of diseases of the myocardium that have a distinct proclivity to ventricular arrhythmias. Of these, ventricular tachycardias pose significant management challenges with the risk of sudden cardiac death and morbidity from multiple causes. Catheter ablation of ventricular tachycardias is becoming an increasingly utilised intervention that has been found to have significant benefits with improving symptoms, reducing anti-arrhythmic drug burden and debilitating device therapies, thereby improving quality of life. Nonetheless, the approach to the ablation of ventricular tachycardias in non-ischemic cardiomyopathies is governed heavily by the disease process, with several distinct differences from ischemic cardiomyopathy including a preponderance to epicardial and deep intramural substrate. This contemporary review aims to present the various disease processes within non-ischemic cardiomyopathies, catheter ablation techniques which have been developed to target ventricular tachycardia and more novel adjunctive therapeutic measures.

Intraprocedure Type II Kounis Syndrome Secondary to Radioiodine Contrast During Coronary Angiography.

An 83-year-old man with a previous right coronary artery (RCA) stent presented to the emergency department with syncope, dynamic lateral ST depression, and a serum troponin of 6148 ng/L (< 17). Coronary angiography revealed a patent proximal RCA stent and significant left-sided disease. The procedure was complicated by inferior ST elevation, urticaria, hypotension, and acute proximal RCA occlusion. This required stenting, which acted as a scaffold to ameliorate subsequent vasospasm that responded to intracoronary glyceryl trinitrate. Serum tryptase postprocedure was markedly elevated at 81.7 µg/L (≤ 11.4) and subsequently normalized. This confirmed a rare presentation of intraprocedural type II Kounis syndrome likely due to radioiodine contrast.