Repeat pulmonary vein isolation and anterior line ablation using a novel point-by-point pulsed-field ablation system.

BACKGROUND: Pulsed-field ablation (PFA) is a nonthermal energy source for ablation of cardiac arrhythmias. This study investigated the prospective outcomes of a novel PFA generator in conjunction with a commercially available, contact force-sensing, focal ablation catheter. OBJECTIVE: The purpose of this study was to assess the feasibility, safety, and lesion characteristics of point-by-point PFA in consecutive patients undergoing repeat ablation of atrial fibrillation (AF). METHODS: The study involved reisolation of pulmonary veins (PVs) with electrical reconnection and the creation of an anterior line (AL) in patients with anterior substrate or durable pulmonary vein isolation (PVI). RESULTS: In 24 patients (46% female; mean age 67 ± 10 years; 67% persistent AF), successful reisolation of 27 of 27 reconnected PVs (100%) was performed. In 19 patients, AL ablation was performed, with bidirectional block in 16 (84%), median ablation time 26 [21, 33] minutes, and first-pass bidirectional block in 13 patients (68%). Acute AL reconduction occurred in 8 of 19 patients (42%). Among these 8 patients, a subsequent sustained block of the AL was achieved in 5 (63%). Ultra-high-density electroanatomic mapping revealed homogeneous but relatively large low-voltage areas in the ablated regions. Median procedural, left atrial dwell, and fluoroscopy times were 100 [90, 109] minutes, 83 [75, 98] minutes, and 10 [8, 13] minutes, respectively. No major or minor complications occurred. CONCLUSION: This study demonstrated feasibility, acute efficacy, and safety of point-by-point PFA for repeat PVI and AL ablation. Further studies are warranted to assess the long-term durability and comparison with established ablation methods.

The infrastructure of electrophysiology centers impacts the management of cardiac tamponade-Results from a national survey.

BACKGROUND: Although electrophysiological (EP) centers have institutional standards, evidence on management of cardiac tamponade is lacking. AIM AND METHODS: A physician-based survey was conducted by sending out questionnaires to all hospitals in Germany performing EP procedures. To evaluate the infrastructure of EP centers and the impact of center volume and onsite cardiac surgery on the management of cardiac tamponade, the results of the survey were analyzed for low-volume (0-250 procedures per year), mid-volume (250-500 procedures), and high-volume (>500 procedures) centers, as well as for centers with and without onsite cardiac surgery. RESULTS: A total of 341 centers were identified and 189/341 (55%) returned data sets were analyzed. Most types of EP procedures are performed across all kinds of centers. Ablation of ventricular tachycardia (VT) is concentrated in higher volume centers and in centers with onsite cardiac surgery. None of the participating low-volume centers and only 13% of centers without onsite cardiac surgery responded to performing epicardial VT ablation. Irrespective of center volume and onsite cardiac surgery, neither body mass index nor age was reported to be an exclusion criterion for ablation procedures. Higher volume centers and centers with onsite cardiac surgery more often have dedicated EP laboratories and EP-nursing teams. Also, differences regarding periprocedural safety precautions and management of cardiac tamponade were found for low-, mid-, and high-volume centers, as well as for centers with and without onsite cardiac surgery. CONCLUSION: While center volume and onsite cardiac surgery do not impact patient selection, there are differences in ablation spectrum, infrastructure, periprocedural safety precautions, and treatment of tamponade.

Acute lesion extension following pulmonary vein isolation with two novel single shot devices: Pulsed field ablation versus multielectrode radiofrequency balloon.

INTRODUCTION: Pulsed-field ablation (PFA) and the multielectrode radiofrequency balloon (RFB) are two novel ablation technologies to perform pulmonary vein isolation (PVI). It is currently unknown whether these technologies differ in lesion formation and lesion extent. We compared the acute lesion extent after PVI induced by PFA and RFB by measuring low-voltage area in high-density maps and the release of biomolecules reflecting cardiac injury. METHODS: PVI was performed with a pentaspline catheter (FARAPULSE) applying PFA or with the compliant multielectrode RFB (HELIOSTAR). Before and after PVI high-density mapping with CARTO 3 was performed. In addition, blood samples were taken before transseptal puncture and after post-PVI remapping and serum concentrations of high-sensitive Troponin I were quantified by immunoassay. RESULTS: Sixty patients undergoing PVI by PFA (n = 28, age 69 ± 12 year, 60% males, 39.3% persistent atrial fibrillation [AF]) or RFB (n = 32, age 65 ± 13 year, 53% males, 21.9% persistent AF) were evaluated. Acute PVI was achieved in all patients in both groups. Mean number of PFA pulses was 34.2 ± 4.5 and mean number RFB applications was 8.5 ± 3 per patient. Total posterior ablation area was significantly larger in PFA (20.7 ± 7.7 cm²) than in RFB (7.1 ± 2.09 cm²; p < .001). Accordingly, posterior ablation area for each PV resulted in larger lesions after PFA versus RFB (LSPV 5.2 ± 2.7 vs. 1.9 ± 0.8 cm², LIPV 5.5 ± 2.3 vs. 1.9 ± 0.8 cm², RSPV 4.7 ± 1.9 vs. 1.6 ± 0.5 cm², RIPV 5.3 ± 2.1 vs. 1.6 ± 0.7 cm,² respectively; p < .001). In a subset of 38 patients, increase of hsTropI was higher after PFA (625 ± 138 pg/mL, n = 28) versus RFB (148 ± 36 pg/mL, n = 10; p = .049) supporting the evidence of larger lesion extent by PFA. CONCLUSION: PFA delivers larger acute lesion areas and higher troponin release upon successful PVI than multielectrode RFB-based PVI in this single-center series.

Novel Radiofrequency Balloon Catheter　- Impact of Ablation Parameters on Single-Shot Isolation.

BACKGROUND: A novel multielectrode radiofrequency balloon (RFB) catheter has been released for pulmonary vein isolation (PVI).Methods and Results: In this observational study consecutive patients with drug-refractory paroxysmal or persistent atrial fibrillation (AF) undergoing first-time PVI were enrolled in 2 high-volume ablation centers. All procedures were conducted in conjunction with a 3D-mapping system. Clinical, procedural and ablation parameters were systematically analyzed. 105 patients (58% male; 52% paroxysmal AF, 68±11.3 years mean age, left atrial volume index 38.6±14.8 mL/m2) were included. 241/412 (58.5%) PVs were successfully isolated with a single shot (SS), with a time-to-isolation of 11.6±8 s. Total number of radiofrequency applications was 892 (mean 2.2/PV), resulting in successful isolation of 408/412 (99%) PVs at the end of the procedure. Mean electrodes' impedance drop was significantly higher in the SS-PVI compared with non-SS applications (21.5±6.6 vs. 18.6±6.5 Ohm). Concordantly, higher temperature rise was observed in the SS vs. non-SS applications (10.9±4.9℃ vs. 9.6±4.7℃). CONCLUSIONS: In this multicenter real-world study, mean impedance drop and temperature rise were associated with successful SS-PVI applying the novel RFB catheter. These parameters may help to guide efficient usage of the new RF balloon.

A novel saline-based occlusion tool allows for dye-less cryoballoon-based pulmonary vein isolation and fluoroscopy reduction.

Background: Cryoballoon (CB)- based pulmonary vein isolation (PVI) remains guided by fluoroscopy and dye. The novel saline injection-based occlusion tool allows for pulmonary vein (PV)-occlusion assessment without the need for dye injection. Aim: To compare KODEX-EPD guided CB-PVI using the novel saline injection-based workflow with conventional cryoablation for acute efficacy, fluoroscopy exposure and dye volume. Methods: Consecutive atrial fibrillation (AF)- patients undergoing CB-PVI in conjunction with KODEX-EPD (CryoEPD group) were analyzed. Patients undergoing conventional CB-PVI (Cryo group) in the same time period acted as controls. Results: One hundred forty patients [91/140 (65%) persistent AF] were studied. Seventy patients underwent CryoEPD procedures [64 ± 13 years, 21 (30%) female] and seventy patients underwent Cryo procedures [68 ± 10 years, 27 (39%) female].A total of 560 PVs were identified and successfully isolated. Mean procedure time was 66 ± 15 min for the CryoEPD group, and 65 ± 19 min for the Cryo group (p = 0.3). Fluoroscopy time (CryoEPD 6 ± 4 min; Cryo 13 ± 6 min, p < 0.001) and dose area product (CryoEPD 193 [111; 297] cGycm2; Cryo 381 [268; 614] cGycm2, p < 0.001) were lower in patients undergoing CryoEPD compared with Cryo procedures. No dye was needed in the CryoEPD group while 53 ± 18 ml dye per patient were administered for the Cryo group (p < 0.001). The overall complication rate was comparable between both groups (p = 0.5). Conclusion: KODEX-EPD guided AF-ablation enables dye-free CB-based PVI with reduced fluoroscopy exposure when compared to conventional CB-ablation, without differences in acute procedural outcomes or procedure duration.

Immunometabolic interference between cancer and COVID-19.

Even though cancer patients are generally considered more susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the mechanisms driving their predisposition to severe forms of coronavirus disease 2019 (COVID-19) have not yet been deciphered. Since metabolic disorders are associated with homeostatic frailty, which increases the risk of infection and cancer, we asked whether we could identify immunometabolic pathways intersecting with cancer and SARS-CoV-2 infection. Thanks to a combined flow cytometry and multiomics approach, here we show that the immunometabolic traits of COVID-19 cancer patients encompass alterations in the frequency and activation status of circulating myeloid and lymphoid subsets, and that these changes are associated with i) depletion of tryptophan and its related neuromediator tryptamine, ii) accumulation of immunosuppressive tryptophan metabolites (i.e., kynurenines), and iii) low nicotinamide adenine dinucleotide (NAD+) availability. This metabolic imbalance is accompanied by altered expression of inflammatory cytokines in peripheral blood mononuclear cells (PBMCs), with a distinctive downregulation of IL-6 and upregulation of IFNγ mRNA expression levels. Altogether, our findings indicate that cancer not only attenuates the inflammatory state in COVID-19 patients but also contributes to weakening their precarious metabolic state by interfering with NAD+-dependent immune homeostasis.

Long-term prognostic impact of subclinical myocardial dysfunction in patients recovered from COVID-19.

BACKGROUND: Cardiovascular sequelae may occur in patients recovered from coronavirus disease 2019 (COVID-19). Recent studies have detected a considerable incidence of subclinical myocardial dysfunction-assessed with speckle-tracking echocardiography-and of long-COVID symptoms in these patients. This study aimed to define the long-term prognostic role of subclinical myocardial dysfunction and long-COVID condition in patients recovered from COVID-19 pneumonia. METHODS: We prospectively followed up 110 patients hospitalized at our institution due to COVID-19 pneumonia in April 2020 and then recovered from SARS-CoV-2 infection. A 7-month clinical and echocardiographic evaluation was performed, followed by a 21-month clinical follow-up. The primary outcome was major adverse cardiovascular events (MACE), a composite of myocardial infarction, stroke, heart failure hospitalization, and all-cause mortality. RESULTS: A subclinical myocardial dysfunction-defined as an impairment of left ventricular global longitudinal strain (≥-18%)-was identified at a 7-month follow-up in 37 patients (34%), was associated with an increased risk of long-term MACE with a good discriminative power (area under the curve: .73) and resulted in a strong independent predictor of extended MACE in multivariate regression analyses. Long-COVID condition was not associated with a worse long-term prognosis, instead. CONCLUSIONS: In patients recovered from COVID-19 pneumonia, a subclinical myocardial dysfunction is present in one-third of the whole population at 7-month follow-up and is associated with a higher risk of MACE at long-term follow-up. Speckle-tracking echocardiography is a promising tool to optimize the risk-stratification in patients recovered from COVID-19 pneumonia, while the definition of a long-COVID condition has no prognostic relevance.

Efficacy and safety in patients treated with a novel radiofrequency balloon: a two centres experience from the AURORA collaboration.

AIMS: A novel irrigated radiofrequency (RF) balloon (RFB) for pulmonary vein (PV) isolation (PVI) was released in selected centres. We pooled the procedural data on efficacy and safety of RFB-PVI from two high volume German centres. METHODS AND RESULTS: Consecutive patients with RFB procedures were enrolled. A 3D electroanatomical left atrial map guided the RFB navigation. Every RF delivery lasted 60 s, and duration was automatically reduced to 20 s for electrodes facing the posterior wall. Procedural data and post-procedural endoscopy data (<48 h) were analysed. Data from 140 patients were collected (57% male, 67 ± 11 years, 57% paroxysmal atrial fibrillation). There were 547 PVs identified, and 99.1% could be isolated using solely the RFB. Single-shot PVI was recorded in 330/547 (60%) PVs. Median time to isolation during the first application was 10 s (IQR 8-13). A total of 2.1 ± 1.8 applications per PV were delivered, with the left superior PV requiring more application compared to other PVs. Median procedure and fluoroscopy time were 77 min (61-99) and 13 min (10-17), respectively. Major safety events were recorded only in the first 25 cases at each centre and included 1/140(0.7%) cardiac tamponade, 1/140(0.7%) phrenic nerve palsy, and 2/140 strokes (1.4%). An oesophageal temperature rise was recorded in 81/547 (15%) PVs, and endoscopy detected oesophageal lesions in 7/85 (8%) patients undergoing endoscopy. CONCLUSION: The RFB showed a high efficacy allowing for fast PVI procedures, and 60% of PVs could be isolated at the first application. Most safety events were recorded during the learning phase. An oesophageal temperature monitoring is suggested: oesophageal lesions were detected in 8% of patients.

Pulsed-field ablation-based pulmonary vein isolation: acute safety, efficacy and short-term follow-up in a multi-center real world scenario.

PURPOSE: Pulsed-field ablation (PFA) is a new energy source to achieve pulmonary vein isolation (PVI) by targeted electroporation of cardiomyocytes. Experimental and controlled clinical trial data suggest good efficacy of PFA-based PVI. We aimed to assess efficacy, safety and follow-up of PFA-based PVI in an early adopter routine care setting. METHODS: Consecutive patients with symptomatic paroxysmal or persistent atrial fibrillation (AF) underwent PVI using the Farawave® PFA ablation catheter in conjunction with three-dimensional mapping at two German high-volume ablation centers. PVI was achieved by applying 8 PFA applications in each PV. RESULTS: A total of 138 patients undergoing a first PVI (67 ± 12 years, 66% male, 62% persistent AF) were treated. PVI was achieved in all patients by deploying 4563 applications in 546 PVs (8.4 ± 1.0/PV). Disappearance of PV signals after the first application was demonstrated in 544/546 PVs (99.6%). More than eight PFA applications were performed in 29/546 PVs (6%) following adapted catheter positioning or due to reconnection as assessed during remapping. Mean procedure time was 78 ± 22 min including pre- and post PVI high-density voltage mapping. PFA catheter LA dwell-time was 23 ± 9 min. Total fluoroscopy time and dose area product were 16 ± 7 min and 505 [275;747] cGy*cm2. One pericardial tamponade (0.7%), one transient ST-elevation (0.7%) and three groin complications (2.2%) occurred. 1-year follow-up showed freedom of arrhythmia in 90% in patients with paroxysmal AF (n = 47) and 60% in patients with persistent AF (n = 82, p = 0.015). CONCLUSIONS: PFA-based PVI is acutely highly effective and associated with a beneficial safety and low recurrence rate.

Temperature-controlled ablation of the mitral isthmus line using the novel DiamondTemp ablation system.

Background: The novel DiamondTemp™ (DT)-catheter (Medtronic®) was designed for high-power, short-duration ablation in a temperature-controlled mode. Aim: To evaluate the performance of the DT-catheter for ablation of the mitral isthmus line (MIL) using two different energy dosing strategies. Materials and methods: Twenty patients with recurrence of atrial fibrillation (AF) and/or atrial tachycardia (AT) following pulmonary vein (PV) isolation were included. All patients underwent reisolation of PVs in case of electrical reconnection and ablation of a MIL using the DT-catheter. Application durations of 10 (group A, n = 10) or 20 s (group B, n = 10) were applied. If bidirectional block was not reached with endocardial ablation, additional ablation from within the coronary sinus (CS) was conducted. Results: In 19/20 (95%) patients, DT ablation of the MIL resulted in bidirectional block. Mean procedure and fluoroscopy time, and dose area product did not differ significantly between the two groups. In group B, fewer radiofrequency applications were needed to achieve bidirectional block of the MIL when compared to group A (26 ± 12 vs. 42 ± 17, p = 0.04). Ablation from within the CS was performed in 8/10 patients (80%) of group A and in 5/10 (50%) patients of group B (p = 0.34). No major complication occurred. Conclusion: Mitral isthmus line ablation with use of the DT-catheter is highly effective and safe. Longer radiofrequency-applications appear to be favorable without compromising safety.

Cryoballoon ablation guided by a novel wide-band dielectric imaging system.

Background and aim: To investigate the feasibility, acute efficacy, periprocedural safety, and procedural parameters of CB-based PVI guided by KODEX-EPD using different occlusion tool software versions. Methods and results: A total of 173 patients (60/173 (35%) paroxysmal AF, 64 ± 12 years, 66/173 (38%) female), underwent CB-based PVI guided by KODEX-EPD between August 2019 and October 2021. Acute PVI was achieved in all the patients. Total fluoroscopy time and dye volume were 13.9 [10.6-19.4] min and 47.5 [20-70] ml. Periprocedural complications occurred in 3 (2%) of the 173 patients. As part of the continued development program, different software versions were used, including 1.4.6 on 38 (22%), 1.4.6a on 33 (19%), 1.4.7 on 41 (24%), and 1.4.8 on 61 (35%) of the patients. Outcomes were compared between software versions by a univariate analysis. Sensitivity analyses were performed to account for confounders. Median fluoroscopy time was decreased by 6.4 min (37.3%), and the median volume of dye was decreased by 32.5 ml (52%) from versions 1.4.6 to 1.4.8. Software version was a significant predictor of fluoroscopy time and dye volume, while reductions in procedure duration and dose area product were observed but mainly explained via confounders. Conclusion: CB-based PVI guided by KODEX-EPD is feasible and safe. Progressive software improvements appear to be associated with lower fluoroscopy duration and dye use. Further studies are needed to evaluate the advantage of KODEX-EPD-guided compared to conventional CB-PVI.

Ablation of Outflow Tract Arrhythmias in Patients With and Without Structural Heart Disease-A Comparative Analysis.

Introduction: Catheter ablation of ventricular arrhythmias emerging from the ventricular outflow tracts and adjacent structures is very effective and considered almost curative in patients without structural heart disease (SHD). Outcomes of patients with SHD undergoing ablation of outflow tract arrhythmias are not known. Methods: Consecutive patients (2019-2021) undergoing catheter ablation of ventricular arrhythmias in a single high-volume center were retrospectively analyzed. Patients with ablation of outflow tract arrhythmias were identified and divided in individuals with and without SHD. Procedural parameters and acute outcome were compared. Results: We identified 215 patients with outflow tract arrhythmias (35.3% female, mean age 58.3 ± 16.0 years). Of those, 93 (43.3%) had SHD. Patients with SHD and outflow tract arrhythmias were older (65.0 ± 12.8 vs. 53.3 ± 16.3 years; p < 0.001), more often male (82.8 vs. 50.0%; p < 0.001) and had more comorbidities than patients without SHD (arterial hypertension: 62.4 vs. 34.4%, p < 0.001; diabetes: 22.6 vs. 8.2%, p = 0.005; chronic lung disease: 20.4 vs. 7.4%, p = 0.007). Outflow tract arrhythmias in patients with SHD had their origin more often in the left ventricle (68.8 vs. 53.3%, p = 0.025). The acute success rate was similar in both patient groups (93.4 vs. 94.2%, p = 0.781). Patients with SHD were discharged later {median length of hospital stay with SHD 5 [6 (interquartile range)] days, without SHD 2 [4] days, p < 0.001}. Periprocedural complications were numerically more frequent in patients with SHD [with SHD 12 (12.9%), without SHD 8 (6.6%), p = 0.154]. Conclusion: Outflow tract arrhythmia ablation has a high success rate irrespective of the presence of SHD. Longer hospital stay and potentially a higher risk of periprocedural complications should be considered when discussing this treatment option with patients.

Migratory and anti-fibrotic programmes define the regenerative potential of human cardiac progenitors.

Heart regeneration is an unmet clinical need, hampered by limited renewal of adult cardiomyocytes and fibrotic scarring. Pluripotent stem cell-based strategies are emerging, but unravelling cellular dynamics of host-graft crosstalk remains elusive. Here, by combining lineage tracing and single-cell transcriptomics in injured non-human primate heart biomimics, we uncover the coordinated action modes of human progenitor-mediated muscle repair. Chemoattraction via CXCL12/CXCR4 directs cellular migration to injury sites. Activated fibroblast repulsion targets fibrosis by SLIT2/ROBO1 guidance in organizing cytoskeletal dynamics. Ultimately, differentiation and electromechanical integration lead to functional restoration of damaged heart muscle. In vivo transplantation into acutely and chronically injured porcine hearts illustrated CXCR4-dependent homing, de novo formation of heart muscle, scar-volume reduction and prevention of heart failure progression. Concurrent endothelial differentiation contributed to graft neovascularization. Our study demonstrates that inherent developmental programmes within cardiac progenitors are sequentially activated in disease, enabling the cells to sense and counteract acute and chronic injury.

Sequential Defects in Cardiac Lineage Commitment and Maturation Cause Hypoplastic Left Heart Syndrome.

BACKGROUND: Complex molecular programs in specific cell lineages govern human heart development. Hypoplastic left heart syndrome (HLHS) is the most common and severe manifestation within the spectrum of left ventricular outflow tract obstruction defects occurring in association with ventricular hypoplasia. The pathogenesis of HLHS is unknown, but hemodynamic disturbances are assumed to play a prominent role. METHODS: To identify perturbations in gene programs controlling ventricular muscle lineage development in HLHS, we performed whole-exome sequencing of 87 HLHS parent-offspring trios, nuclear transcriptomics of cardiomyocytes from ventricles of 4 patients with HLHS and 15 controls at different stages of heart development, single cell RNA sequencing, and 3D modeling in induced pluripotent stem cells from 3 patients with HLHS and 3 controls. RESULTS: Gene set enrichment and protein network analyses of damaging de novo mutations and dysregulated genes from ventricles of patients with HLHS suggested alterations in specific gene programs and cellular processes critical during fetal ventricular cardiogenesis, including cell cycle and cardiomyocyte maturation. Single-cell and 3D modeling with induced pluripotent stem cells demonstrated intrinsic defects in the cell cycle/unfolded protein response/autophagy hub resulting in disrupted differentiation of early cardiac progenitor lineages leading to defective cardiomyocyte subtype differentiation/maturation in HLHS. Premature cell cycle exit of ventricular cardiomyocytes from patients with HLHS prevented normal tissue responses to developmental signals for growth, leading to multinucleation/polyploidy, accumulation of DNA damage, and exacerbated apoptosis, all potential drivers of left ventricular hypoplasia in absence of hemodynamic cues. CONCLUSIONS: Our results highlight that despite genetic heterogeneity in HLHS, many mutations converge on sequential cellular processes primarily driving cardiac myogenesis, suggesting novel therapeutic approaches.

Disentangling the Association of Hydroxychloroquine Treatment with Mortality in Covid-19 Hospitalized Patients through Hierarchical Clustering.

The efficacy of hydroxychloroquine (HCQ) in treating SARS-CoV-2 infection is harshly debated, with observational and experimental studies reporting contrasting results. To clarify the role of HCQ in Covid-19 patients, we carried out a retrospective observational study of 4,396 unselected patients hospitalized for Covid-19 in Italy (February-May 2020). Patients' characteristics were collected at entry, including age, sex, obesity, smoking status, blood parameters, history of diabetes, cancer, cardiovascular and chronic pulmonary diseases, and medications in use. These were used to identify subtypes of patients with similar characteristics through hierarchical clustering based on Gower distance. Using multivariable Cox regressions, these clusters were then tested for association with mortality and modification of effect by treatment with HCQ. We identified two clusters, one of 3,913 younger patients with lower circulating inflammation levels and better renal function, and one of 483 generally older and more comorbid subjects, more prevalently men and smokers. The latter group was at increased death risk adjusted by HCQ (HR[CI95%] = 3.80[3.08-4.67]), while HCQ showed an independent inverse association (0.51[0.43-0.61]), as well as a significant influence of cluster∗HCQ interaction (p < 0.001). This was driven by a differential association of HCQ with mortality between the high (0.89[0.65-1.22]) and the low risk cluster (0.46[0.39-0.54]). These effects survived adjustments for additional medications in use and were concordant with associations with disease severity and outcome. These findings suggest a particularly beneficial effect of HCQ within low risk Covid-19 patients and may contribute to clarifying the current controversy on HCQ efficacy in Covid-19 treatment.