Citations

Introduction: Most of long QT syndrome (LQTS) is explained by pathogenic variants in KCNQ1 , KCNH2 , or SCN5A . However, ~10-20% of LQTS index cases remain genetically elusive following commercial genetic testing. Here, we identified and functionally characterized a novel LQTS genetic substrate in a multi-generational, “genotype negative” LQTS pedigree. Methods: The index case was a 40-year-old female with a history of syncope, seizures, ventricular fibrillation, and a family history of LQTS and sudden death. Although anticipated to have KCNH2- mediated LQT2, commercial genetic testing of all LQTS-causative genes was negative. Genome sequencing and variant analysis was performed on 6 affected family members. Patient-specific and CRISPR/Cas9 “gene-corrected” isogenic control induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were generated. RT-PCR was used to determine the effects of the identified variant on splicing. Action potential duration (APD) and field potential duration (FPD) were measured using voltage-sensing dye (Fluovolt) and microelectrode array, respectively. Results: No ultra-rare, nonsynonymous heterozygous variants co-segregated among the 6 LQTS phenotype-positive individuals. Instead, a deep intronic KCNH2 variant (c.3331-316 G>T) was present in all affected individuals. RT-PCR analysis of patient-specific iPSC-CM-derived RNA revealed that c.3331-316 G>T creates a novel 89 base-pair exon residing between canonical exons 14 and 15 of KCNH2 that results in a frame-shift variant annotated as p.S1112Pfs*171. The APD 90 was significantly longer in p.S1112Pfs*171-iPSC-CMs (647 ± 12 ms, n=50) compared to isogenic control iPSC-CMs (412 ± 10 ms, n=50, p < 0.0001). Further, the FPD was significantly longer in p.S1112Pfs*171-iPSC-CMs (349 ± 8 ms, n=48) compared to isogenic control iPSC-CMs (209 ± 10 ms, n=20, p < 0.0001). Conclusions: A novel deep intronic KCNH2 variant was identified in a multi-generational genetically elusive LQTS pedigree. The patient-derived and isogenic control iPSC-CMs establish that the p.S1112Pfs*171-KCNH2 variant is the monogenetic cause for this family’s LQTS. As suggested by the phenotype, this family indeed has KCNH2 -mediated LQT2 albeit stemming from a deep intronic variant .

Introduction: Long QT syndrome (LQTS) is an autosomal dominant disorder characterized by a prolonged QT interval on a 12-lead electrocardiogram (ECG). Cascade genetic testing for LQTS is standard of care, including in infants, but takes 2-4 weeks for return of results. For newborns of parent with confirmed LQTS, the ECG is obtained after birth as an initial assessment, but QTc values during the immediate newborn period may be misleading. Thus, our objective was to determine the ECG’s diagnostic accuracy in the first 48 hours of life for neonates born to a parent with LQTS. Methods: We performed a retrospective review of the electronic medical records of neonates born to a parent with ≥ 1 pathogenic variant in a LQTS-causative gene for which at least 1 ECG in the first 48 hours of life was obtained. Clinical data was collected on all neonates with focus on the 12-lead ECG, family history, and genetic testing results. The sensitivity and specificity of the diagnostic ECG were calculated using QTc thresholds of 440, 460, and 470 ms. Results: Overall, 70 infants (35 [50%] females) met inclusion criteria and the mean QTc on the first ECG was 484 ± 61 ms. Following genetic testing, a LQTS-causing variant was identified in 46 infants (66%), including 22 (48%) with LQT1 ( KCNQ1 ), 12 (26%) with LQT2 ( KCNH2 ), and 8 (17%) with LQT3 ( SCN5A ). Mean QTc in the first 48 hours of life for neonates that ultimately were genotype-positive was 502 ± 59 ms compared to 451 ± 50 ms (p < 0.001) for genotype-negative neonates. When using a recommended threshold QTc of ≥ 440 ms, 6/46 genotype-positive neonates (13%) were missed (underdiagnosed) and 13/24 genotype-negative neonates (54%) were overdiagnosed (sensitivity: 87%, specificity: 45%). At a QTc threshold ≥ 460 ms, 15 (21%) were classified erroneously (sensitivity: 85%, specificity: 67%) while at a threshold of ≥ 470 ms, 18 (26%) were misclassified (sensitivity: 76%, specificity: 71%). Conclusions: Although a baseline ECG should still be obtained before a newborn’s dismissal, reliance solely on the QTc for diagnosing LQTS and initiating therapy will result in an unacceptable number of misclassifications. Thus, genetic testing must be initiated prior to the baby’s discharge and proper anticipatory guidance is vital while awaiting genetic test results.

Introduction: Type 2 long QT syndrome (LQT2) is caused by loss-of-function variants in the KCNH2 -encoded K v 11.1 potassium channel which is essential for the rapid delayed rectifier channel (I Kr ) that governs phase 3 of cardiac action potential (AP). No current therapies target the molecular cause of LQT2. Methods: A dual-component “suppression-and-replacement” (SupRep) KCNH2 gene therapy was created by cloning into a single construct a custom-designed KCNH2 shRNA that produces ~80% knockdown (suppression) and a “shRNA-immune” (shIMM) KCNH2 cDNA modified by the introduction of synonymous single nucleotide substitutions within the shRNA target site (replacement). The ability of KCNH2-SupRep gene therapy to suppress and replace LQT2-causative variants in KCNH2 was evaluated via heterologous expression in TSA201 cells. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were generated from two patients with LQT2 (KCNH2-G604S and -N633S). CRISPR-Cas9 corrected isogenic control iPSC-CMs were made. Both lines were treated with KCNH2-SupRep or non-targeting control shRNA (shCT). FluoVolt voltage dye was used to measure the APD. Results: KCNH2-SupRep achieved mutation-independent suppression of wild-type KCNH2 and both LQT2-causative variants with simultaneous replacement of KCNH2-shIMM as measured by allele-specific qRT-PCR. Treatment with KCNH2-SupRep resulted in shortening of the pathologically prolonged APD at 90% repolarization (APD 90 ) to near isogenic control APD 90 levels (G604S: isogenic controls, 424 + 39 ms and N633S: isogenic controls, 433 + 16 ms) compared to treatment with non-targeting shCT (G604S: SupRep treated, 399±105 ms vs. shCT treated, 577±39 ms, p<0.0001; N633S: SupRep treated, 432±85 ms vs. shCT treated, 483±65 ms, p<0.005). Conclusions: We provide the first proof-of-principle gene therapy for correction of LQT2. Like our sentinel discovery of SupRep gene therapy for LQT1, KCNH2-SupRep successfully suppressed and replaced KCNH2 to normal wild-type levels. In TSA201 cells, co-transfection of LQT2 variants and KCNH2-SupRep caused mutation-independent suppression-and-replacement of KCNH2 . In LQT2 iPSC-CMs, KCNH2-SupRep shortened the APD, thereby eliminating the pathognomonic feature of LQT2.

Introduction: Bioprosthetic valve thrombosis (BPVT) is a well-recognized cause of prosthetic dysfunction. Anticoagulation restores prosthetic valve gradients, but long term outcomes and complications from therapy are unknown. Objectives: To define the complications and long-term outcomes of anticoagulant therapy for BPVT. Methods: Retrospective matched cohort study of patients treated with warfarin for presumed BPVT at a single center from 1999 to 2016. Controls with normal bioprostheses by echocardiography were matched 2:1 for age at implantation, gender, prosthetic valve position, and type of prosthesis (porcine / pericardial). Results: A total of 83 presumed BPVT patients (40 aortic, 21 mitral, 18 tricuspid, and 4 pulmonary) and 166 controls were included. Age at BPVT diagnosis was 60±19 yrs (41±41 months post implantation); 45 (54%) were male. Transvalvular gradients returned to baseline in 63 (76%) of the patients, after 5±4 months of warfarin; 60 (72%) patients were maintained on warfarin indefinitely. Recurrent BPVT was seen in 13 (16%) patients, 33±31 months after initial therapy. When compared to controls, warfarin-treated BPVT patients had similar incidence of stroke [4(5%) vs 5 (3%), p=0.49], peripheral embolic events [4(5%) vs 10 (6%), p=0.78)], and death [12 (14%) vs 28 (17%), p= 0.72] (Figure, left panel), but more bleeding requiring transfusion [18 (22%) vs 3 (2%), p<0.0001]. Presumed BPVT patients more often required surgical or percutaneous valve re-replacement (Figure, center panel); this difference persisted even when comparing only patients with confirmed BPVT (those who responded to anticoagulant therapy) vs. their matched controls (Figure, right panel). Conclusion: Warfarin anticoagulation for presumed BPVT is successful in the majority of patients, without increase in stroke, peripheral embolism or death, but at the cost of excess bleeding. Recurrent BPVT occured in 16% of patients. Importantly, patients with BPVT required more often valve re-replacement. This finding suggests that anticoagulant therapy does not fully restore prosthetic valve durability, and that BPVT patients should be closely monitored.

Introduction: Studies have demonstrated an association between hyperkalemia and increased mortality in patients with myocardial infarction, but limited data exist regarding hyperkalemia and associated death among unselected cardiac intensive care unit (CICU) patients. Hypothesis: Hyperkalemia is associated with mortality in CICU patients. Methods: Historical cohort of 9,681 CICU patients admitted from January 2007 to December 2015 with serum potassium measured on admission. Hyperkalemia was defined as admission potassium >=5.0 mEq/L, normokalemia as admission potassium 3.5-4.9 mEq/L, and hypokalemia as admission potassium <3.5 mEq/L. Multivariate logistic regression was used to determine predictors of hospital mortality. Post-discharge survival was assessed using Kaplan-Meier analysis and Cox proportional hazards models. Results: Mean age was 67±15 years with 3,629 (36%) females and hospital mortality of 9%. Hyperkalemia occurred in 1,187 (12.3%), and hypokalemia occurred in 719 (7.4%). Compared to normokalemic patients, both hyperkalemic patients (unadjusted OR 2.85, 95% CI 2.40-3.39; P<.001) and hypokalemic patients (unadjusted OR 2.31, 95% CI 1.85-2.88; P<.001) were at increased risk of hospital mortality. After adjustment for illness severity and renal function, only hyperkalemic patients were at increased risk of hospital death (adjusted OR 1.35, 95% CI 1.07-1.69; p = 0.01), while hypokalemic patients were not (P = NS). Among hospital survivors, hyperkalemic patients had lower post-discharge survival by Kaplan-Meier analysis (P <0.001), while hypokalemic patients had similar survival compared to normokalemic patients (p = NS). After adjustment for illness severity and renal function, hospital survivors with hyperkalemia were at increased risk for post-discharge mortality compared with normokalemic patients (adjusted HR 1.16, 95% CI 1.05-1.28; p=.003). Conclusions: Hyperkalemia on CICU admission is associated with higher hospital and post-discharge mortality, independent of renal function and illness severity. This emphasizes the importance of potassium abnormalities as a risk predictor in patients admitted to the CICU.

Introduction: Loss-of-function (LOF) variants in the KCNH2 -encoded Kv11.1 potassium channel cause type 2 long QT syndrome (LQT2). To date, hundreds of KCNH2 missense variants (MVs) have been published as “disease-causative”. However, it has been suggested that 10% of rare LQTS variants in the literature may be "false positives”. Objective: To determine previously published KCNH2 variants that are likely false positives and warrant demotion to at least likely benign status. Methods: A list of all case-derived LQT2-associated MVs from six large published compendia was compiled. The frequency of each MV within the Genome Aggregation Database (gnomAD, n = 141,352 individuals) was recorded. Eight in silico variant assessment tools were used to grade each MV. Variants (n=8) absent in gnomAD but predicted “benign” by all 8 tools were considered potential false positives, despite being ultra-rare, and were characterized functionally using whole-cell patch clamp. Results: Overall, 339 KCNH2 MVs were identified among LQTS cases. Of these, 13 (4%) were seen at a minor allele frequency (MAF) > 0.0004 in gnomAD. This MAF cut-off is derived from the frequency of R176W-KCNH2, a well-established albeit weakly penetrant (i.e. < 20%) LQT2-causative MV. Variants seen at MAF > R176W-KCNH2 are unlikely to be LQT2-contributing. However, 253 MVs (75%) were absent in gnomAD. Of these, 8 (4%) MVs (I96V, G187S, A203T, P241L, H254Q, G314S, P935S, and P963T) were predicted by all 8 in silico tools to be benign and had never been characterized functionally. Patch clamp studies did not demonstrate any LOF perturbation for these 8 MVs. Conclusion: This study offers compelling evidence for the demotion from LQT2-causative status to likely benign status for 21 (6%) of the 339 previously published LQT2 MVs based either on i) gnomAD MAF unacceptably high for a 1:8000 disorder (LQT2) for 13 MVs or ii) ultra-rarity (never seen in gnomAD) but in silico variant assessment tools predicting benign impact of the amino acid substitution and in vitro functional validation studies devoid of LOF for 8 additional MVs. This meticulous “pruning” exercise must be conducted for all published variants previously implicated as the monogenic cause for LQTS in particular and all genetic heart diseases in general.

Background: The aim of this study was to determine whether adding DE-CMR and/or TTE based parameters beyond known clinical factors provides incremental improvement of predicting long-term outcomes in STEMI patients who undergo acute reperfusion therapy. Methods and Results: One hundred twenty patients with first time STEMI who underwent PCI (74%), fibrinolysis (3%), and both (19%), were studied by both delayed enhancement cardiac magnetic resonance (DE-CMR) and transthoracic echocardiogram (TTE) during the acute phase of myocardial infarction. The primary endpoint was major adverse cardiac events (MACE). There were 28 events (6 deaths, 13 recurrent ischemia, and 9 heart failure) over a median follow-up of 4 years. We defined incremental increase in prognostic value by increase in Cox proportional hazards global chi square (χ 2 ) and/or increase in c-index with the addition of TTE and/or CMR parameters after adjusting for clinical variables. Among the clinical data, heart rate (HR: 1.02, p=0.047) and troponin (HR: 1.13, p=0.013) predicted MACE (χ 2 : 12.4, P=0.002; C index 0.69). After adjusting for these clinical factors, adding TTE parameters (left ventricular end systolic volume index [HR: 1.05, p<0.0001] and mitral valve deceleration time [HR: 0.99, p=0.036]), increased the global χ 2 to 24.6 and C index to 0.74 (p<0.0001). When CMR parameter (infarct size [HR: 2.92, p<0.0001]) was added to the clinical data alone, there was greater increase in global χ 2 to 36.8 and C index to 0.83 (p<0.0001). Addition of DE- CMR to clinical data combined with TTE measures showed significant incremental value with increased χ 2 difference of 17.6 (p<0.0001). There was no significant incremental value of adding TTE to clinical data combined with DE-CMR (p>0.05). Conclusion: DE-CMR provides significant incremental value for prognosticating adverse cardiac events over clinical data alone (or when in combination with TTE) in STEMI patients who undergo reperfusion therapy.

Background: Shock is a highly dreaded complication of type A acute aortic dissection (TAAAD). However, few data exist on its incidence and association with prognosis. Methods: We evaluated 2704 TAAAD patients [mean age 61.4 ± 14.5, (67.6%) male] from the International Registry of Acute Aortic Dissection. Results: Shock was present at arrival in 407 (15.1%) TAAAD patients. These patients demonstrated no difference in age (61.5 ± 15.2 with shock vs. 61.4 ± 14.4 years without; p=0.873), but were more likely to have history of hypertension (83.1% vs. 73.0%; p<0.001), atherosclerosis (36.5% vs. 21.7%, p<0.001) and diabetes (12.3% vs. 7.0%, p=0.001) than patients without shock. They had more surgical management (90.9% vs. 86.0%; p=0.007). In-hospital complications such as hypotension (49.8% vs. 28.6%; p<0.001), coma (11.4% vs. 5.8%; p<0.001), tamponade (33.6% vs. 18.2%; p<0.001) and myocardial ischemia/infarction (19.7% vs. 13.7%; p=0.006) were more common among shock patients. Overall in-hospital mortality (30.2% vs. 23.9%; p=0.007) and mortality by management (surgical: 24.6% vs. 19.1%; p=0.015; medical: 88.9% vs. 53.3%, p<0.001) were higher among shock patients. Independent predictors of in-hospital mortality in shock patients are displayed in Table 1. Among hospital survivors, Kaplan-Meier estimates of follow-up mortality were similar between groups (p=0.609). Conclusions: Shock occurred in 15.1% of patients with TAAAD and was associated with increased in-hospital morbidity and mortality, but not long-term mortality.

Background: Concerns exist regarding orthotropic heart transplantation (OHT) in hepatitis C (HCV) seropositive recipients. The UNOS national registry was accessed to evaluate HCV recipient sero-positivity and outcomes. Method: Retrospective analysis of the UNOS registry (2000-2014) to evaluate recipient profile and clinical outcome of HCV sero-positive (HCV+ve) and sero-negative (HCV -ve) pts. Early and late adjusted survival and adverse events at follow-up were compared. Results: From 23,507 patients (mean age 52 yrs; 75% male), 481 (2%) were HCV +ve (mean age 52 yrs; 77% male). Annual proportion of HCV +ve recipients was comparable over the study period (range 1.3-2.7%; p=0.2). The HCV +ve cohort had more African American (22% vs 17%; p=0.01), pts with a prior LVAD (21 vs 14%; p<0.01 and more hepatitis B core Ag+ve recipients (17% vs 5%; p<0.01). However, ECMO (p=0.7), inotropic (p=0.2), and intra-aortic balloon pump (p=0.7) support, serum creatinine (p=0.7) and serum bilirubin (p=0.7) were similar. Proportion of Status 1A pts was similar (24% HCV+ vs 21% HCV -); however wait-time for HCV + recipients was longer (mean 23 vs 19 days; p<0.01). Among donor variables, age (p=0.8), hepatitis B status (p=0.4) and CDC high risk status (p=0.9) were comparable. At a median follow up of 4 years, 67.1% patients were alive, 28.4% died and 1.1% were re-transplanted (3.4% missing). Overall survival was worse in the HCV+ cohort (64.3 vs 72.9 % and 43.2 vs 55% at five and ten years; p<0.01). Late renal [OR 1.2(1-1.6); p = 0.02] and liver dysfunction [OR 4.5 (1.2-15.7); p=0.01] occur in HCV +ve recipients. On adjusted analysis, HCV sero-positivity is associated with poorer survival [HR0.6 (0.5-0.8); p<0.01]. Conclusion: A small proportion of patients receiving a heart transplant in the United States have hepatitis C. In spite of comparable pre-operative hepatic function, hepatitis C sero-positive recipients develop late liver dysfunction and have poorer long-term survival.