Ultra-high-frequency ECG assessment of QRS fragmentation predicts sudden cardiac death risk in inherited arrhythmia syndromes

Background

Fragmentation of the QRS complex, as a surrogate for scar or functionally disrupted ventricular activation, has been postulated as a risk factor for malignant ventricular arrhythmias across a range of cardiac diagnoses including cardiomyopathies, channelopathies and myocardial infarction. Fragmentation is subtle on the conventionally filtered 12-lead ECG and can easily be missed or over-diagnosed. Isolation of high-frequency (HF) QRS components could overcome this to demonstrate easily identifiable fragmentation but this has previously been limited by technological constraints resulting in a limited range of measured frequencies (150–300Hz). Ultra-high-frequency ECG (UHF-ECG) is a novel technology that utilises amplification and signal-averaging techniques to reliably measure frequencies up to 1000Hz.

Purpose

We explored the use of UHF-ECG in arrhythmia risk stratification.

Methods

We recruited 60 participants to undergo UHF-ECG recordings, including 23 healthy volunteers and 37 patients with inherited arrhythmia syndromes: 25 hypertrophic cardiomyopathy (HCM), 5 Brugada syndrome, 4 arrhythmogenic cardiomyopathy, 3 idiopathic ventricular fibrillation, 2 long QT syndrome and 1 non-ischaemic dilated cardiomyopathy.

The arrhythmia risk status of patients with inherited disease was classified, by two independent researchers, into high or low risk based on their history of cardiac arrest, sustained ventricular arrhythmia, appropriate therapy, syncope and programmed ventricular stimulation result. A third researcher adjudicated disagreement. Two further researchers, blinded to aforementioned risk status, independently assessed the UHF-ECG recordings of all participants.

Results

40 patients were classified as low risk, and 20 as high. Healthy volunteer UHF-ECGs showed uniform ventricular activation with single HF peaks in each lead. High-risk patients' UHF-ECGs showed multiple HF peaks, representing QRS fragmentation. The maximum number of HF peaks in any lead was used to measure severity of fragmentation. Example UHF-ECGs are shown in Figure 1. Fragmentation severity (number of peaks) correlated with arrhythmia risk status (chi-square statistic = 8.95, p-value = 0.03) across all participants (Figure 2) and when comparing high to low risk patients with inherited disease.

UHF-ECG fragmentation could be observed even when the 12-lead ECG did not show any observable fragmentation. Among patients with inherited disease, patients with HCM showed the largest difference in UHF-ECG fragmentation between high and low risk. UHF-ECG fragmentation analysis showed excellent reproducibility with no difference in number of peaks identified between two independent assessors.

Conclusion

We demonstrate proof-of-concept that a novel ultra-high-frequency tool for measuring a broad range of high frequency QRS components can be used for sudden death risk stratification in patients with inherited cardiac conditions.

Funding Acknowledgement

Type of funding sources: None.

Prevalence and diagnostic significance of novel 12-lead ECG patterns following COVID-19 infection in elite soccer players

Background

Identification of athletes with cardiac inflammation following COVID-19 can prevent exercise fatalities. The efficacy of pre and post COVID-19 infection electrocardiograms (ECGs) for detecting athletes with myopericarditis has never been reported. We aimed to assess the prevalence and diagnostic significance of novel 12-lead ECG patterns following COVID-19 infection in elite soccer players.

Methods

We conducted a multicentre study over a 2-year period involving 5 centres and 34 clubs and compared pre COVID and post COVID ECG changes in 455 consecutive athletes. ECGs were reported in accordance with the International recommendations for ECG interpretation in athletes. The following patterns were considered abnormal if they were not detected on the pre COVID-19 infection ECG: (a) biphasic T-waves; (b) reduction in T-wave amplitude by 50% in contiguous leads; (c) ST-segment depression; (d) J-point and ST-segment elevation >0.2 mV in the precordial leads and >0.1 mV in the limb leads; (e) tall T-waves ≥1.0 mV (f) low QRS-amplitude in >3 limb leads and (g) complete right bundle branch block. Athletes exhibiting novel ECG changes underwent cardiovascular magnetic resonance (CMR) scans. One club mandated CMR scans for all 28 (6%) athletes, despite the absence of cardiac symptoms or ECG changes.

Results

Athletes were aged 22±5 years (89% male and 57% white). 65 (14%) athletes reported cardiac symptoms. The mean duration of illness was 3±4 days. The post COVID ECG was performed 14±16 days following a positive PCR. 440 (97%) athletes had an unchanged post COVID-19 ECG. Of these, 3 (0.6%) had cardiac symptoms and CMRs resulted in a diagnosis of pericarditis. 15 (3%) athletes demonstrated novel ECG changes following COVID-19 infection. Among athletes who demonstrated novel ECG changes, 10 (67%) reported cardiac symptoms. 13 (87%) athletes with novel ECG changes were diagnosed with inflammatory cardiac sequelae; pericarditis (n=6), healed myocarditis (n=3), definitive myocarditis (n=2), and possible/probable myocarditis (n=2). The overall prevalence of inflammatory cardiac sequelae based on novel ECG changes was 2.8%. None of the 28 (6%) athletes, who underwent a CMR, in the absence of cardiac symptoms or novel ECG changes revealed any abnormalities. Athletes revealing novel ECG changes, had a higher prevalence of cardiac symptoms (67% v 12% p<0.0001) and longer symptom duration (8±8 days v 2±4 days; p<0.0001) compared with athletes without novel ECG changes. Among athletes without cardiac symptoms, the additional yield of novel ECG changes to detect cardiac inflammation was 20% (n=3).

Conclusions

3% of elite soccer players demonstrated novel ECG changes post COVID-19 infection, of which almost 90% were diagnosed with cardiac inflammation during subsequent investigation. Most athletes with novel ECG changes exhibited cardiac symptoms. Novel ECGs changes contributed to a diagnosis of cardiac inflammation in 20% of athletes without cardiac symptoms.

Funding Acknowledgement

Type of funding sources: None.

Pregnancy related complications in women with hypertrophic cardiomyopathy

OBJECTIVES

To determine whether pregnancy is well tolerated in hypertrophic cardiomyopathy.

SETTING

Referral clinic.

DESIGN

The study cohort comprised 127 consecutively referred women with hypertrophic cardiomyopathy. Forty (31.5%) underwent clinical evaluation before pregnancy. The remaining 87 (68.5%) were referred after their first pregnancy. All underwent history, examination, electrocardiography, and echocardiography. Pregnancy related symptoms and complications were determined by questionnaire and review of medical and obstetric records where available.

RESULTS

There were 271 pregnancies in total. Thirty six (28.3%) women reported cardiac symptoms in pregnancy. Over 90% of these women had been symptomatic before pregnancy. Symptoms deteriorated during pregnancy in fewer than 10%. Of the 36 women with symptoms during pregnancy, 30 had further pregnancies. Symptoms reoccurred in 18 (60%); symptomatic deterioration was not reported. Heart failure occurred postnatally in two women (1.6%). No complications were reported in 19 (15%) women who underwent general anaesthesia and in 22 (17.4%) women who received epidural anaesthesia, three of whom had a significant left ventricular outflow tract gradient at diagnosis after pregnancy. Three unexplained intrauterine deaths occurred in women taking cardiac medication throughout pregnancy. No echocardiographic or clinical feature was a useful indicator of pregnancy related complications.

CONCLUSIONS

Most women with hypertrophic cardiomyopathy tolerate pregnancy well. However, rare complications can occur and therefore planned delivery and fetal monitoring are still required for some patients.

Line bisection in normal adults: direction of attentional bias for near and far space

The direction of attentional bias in forty normal adults was assessed using a computer generated line bisection task. A 4 (viewing distance)x4 (line length)x2 (cursor starting position) repeated measures factorial design was employed. As predicted, differences in bisection performance as a function of viewing distance were observed. The findings confirmed that scanning direction (contingent upon the starting position of the cursor), but not line length, significantly modulated this effect. The direction of bias across near and far space was further clarified yielding a progressive shift from a leftward bias in near space to a rightward bias in far space. A significant interaction of distance, line length and starting position revealed differential effects for left and right starting positions as a function of viewing distance and line length. More specifically, a leftward start witnessed deviations shifting progressively from left-to-right as distance and line length increased though no comparable pattern was observed for rightward starts. The results provide important behavioural support for the suggestion that dissociated neural systems may be responsible for attending and acting in near and far space and that other lateralised functions (such as scanning strategies) can influence hemispheric activation. The findings have relevant theoretical implications as well as important implications for the clinical assessment of unilateral neglect using a standard line bisection task, both of which are discussed.

Sudden death in hypertrophic cardiomyopathy: identification of high risk patients

OBJECTIVES

We sought to identify patients with hypertrophic cardiomyopathy (HCM) at high risk of sudden death (SD).

BACKGROUND

Relatively low mortality rates in HCM make conventional analysis of multiple clinical risk markers for SD problematic. This study used a referral center registry to investigate a smaller number of generally accepted noninvasive risk markers.

METHODS

We studied 368 patients (14 to 65 years old, 239 males) with HCM. There were five variables: nonsustained ventricular tachycardia (NSVT), syncope, exercise blood pressure response (BPR), family history of sudden death (FHSD) and left ventricular wall thickness (LVWT).

RESULTS

During follow-up (3.6+/-2.5 years [range 2 days to 9.6 years]), 36 patients (9.8%) died, 22 of them suddenly. Two patients received heart transplants. The six-year SD-free survival rate was 91% (95% confidence interval [CI] 87% to 95%). In the Cox model, there was a significant pairwise interaction between FHSD and syncope (p = 0.01), and these were subsequently considered together. The multivariate SD risk ratios (with 95% CIs) were 1.8 for BPR (0.7 to 4.4) (p = 0.22); 5.3 for FHSD and syncope (1.9 to 14.9) (p = 0.002); 1.9 for NSVT (0.7 to 5.0) (p = 0.18) and 2.9 for LVWT (1.1 to 7.1) (p = 0.03). Patients with no risk factors (n = 203) had an estimated six-year SD-free survival rate of 95% (95% CI 91% to 99%). The corresponding six-year estimates (with 95% CIs) for one (n = 122), two (n = 36) and three (n = 7) risk factors were 93% (87% to 99%), 82% (67% to 96%) and 36% (0% to 75%), respectively. Patients with two or more risk factors had a lower six-year SD survival rate (95% CI) compared with patients with one or no risk factors (72% [56% to 88%] vs. 94% [91% to 98%]) (p = 0.0001).

CONCLUSIONS

This study demonstrates that patients with multiple risk factors have a substantially increased risk of SD sufficient to warrant consideration for prophylactic therapy.

A new mutation of the cardiac troponin T gene causing familial hypertrophic cardiomyopathy without left ventricular hypertrophy

AIM

To screen for a mutation of the cardiac troponin T gene in two families where there had been sudden deaths without an increase in left ventricular mass but with myocardial disarray suggesting hypertrophic cardiomyopathy.

METHODS

DNA from affected individuals from both families was used to screen the cardiac troponin T gene on an exon by exon basis. Mutation screening was achieved by polymerase chain reaction and direct sequencing. Where appropriate, a mutation was confirmed by restriction digest.

RESULTS

A novel missense mutation of exon 9 was found in the affected individuals of one of the families. This mutation at amino acid 94 resulted in the substitution of arginine for leucine and was not found in 100 normal control samples. A mutation of the cardiac troponin T gene was excluded in the second family.

CONCLUSIONS

A mutation of the gene for the sarcomeric protein cardiac troponin T can cause familial hypertrophic cardiomyopathy with marked myocyte disarray and frequent premature sudden death in the absence of myocardial hypertrophy at clinical or macroscopic level.

Survival after cardiac arrest or sustained ventricular tachycardia in patients with hypertrophic cardiomyopathy

OBJECTIVES

The aim of this study was to evaluate the survival of patients with hypertrophic cardiomyopathy (HCM) after resuscitated ventricular fibrillation or syncopal sustained ventricular tachycardia (VT/VF) when treated with low dose amiodarone or implantable cardioverter defibrillators (ICDs).

BACKGROUND

Prospective data on clinical outcome in patients with HCM who survive a cardiac arrest are limited, but studies conducted before the widespread use of amiodarone and/or ICD therapy suggest that over a third die within seven years from sudden cardiac death or progressive heart failure.

METHODS

Sixteen HCM patients with a history of VT/VF (nine male, age at VT/VF 19 +/- 8 years [range 10 to 36]) were studied. Syncopal sustained ventricular tachycardia/ventricular fibrillation occurred during or immediately after exertion in eight patients and was the initial presentation in eight. One patient had disabling neurologic deficit after VT/VF. Before VT/VF, two patients had angina, four had syncope and six had a family history of premature sudden cardiac death. After VT/VF all patients were in New York Heart Association class I or II, three had nonsustained VT during ambulatory electrocardiography and 11 had an abnormal exercise blood pressure response. After VT/VF eight patients were treated with low dose amiodarone and six received an ICD. Prophylactic therapy was declined by two patients.

RESULTS

Mean follow-up was 6.1 +/- 4.0 years (range 0.5 to 14.5). Cumulative survival (death or ICD discharge) for the entire cohort was 59% at five years (95% confidence interval: 33% to 84%). Thirteen (81%) patients were alive at last follow-up. Two patients died suddenly while taking low dose amiodarone, and one died due to neurologic complications of his initial cardiac arrest. Three patients had one or more appropriate ICD discharges during follow-up; the times to first shock after ICD implantation were 23, 197 and 1,124 days.

CONCLUSIONS

This study shows that patients with HCM who survive an episode of VT/VF remain at risk for a recurrent event. Implantable cardioverter defibrillator therapy appears to offer the best potential benefit regarding outcome.

Association of angiotensin-converting enzyme gene I/D polymorphism with change in left ventricular mass in response to physical training

BACKGROUND

The absence (deletion allele [D]) of a 287-base pair marker in the ACE gene is associated with higher ACE levels than its presence (insertion allele [I]). If renin-angiotensin systems regulate left ventricular (LV) growth, then individuals of DD genotype might show a greater hypertrophic response than those of II genotype. We tested this hypothesis by studying exercise-induced LV hypertrophy.

METHODS AND RESULTS

Echocardiographically determined LV dimensions and mass (n=140), electrocardiographically determined LV mass and frequency of LV hypertrophy (LVH) (n=121), and plasma brain natriuretic peptide (BNP) levels (n=49) were compared at the start and end of a 10-week physical training period in male Caucasian military recruits. Septal and posterior wall thicknesses increased with training, and LV mass increased by 18% (all P<.0001). Response magnitude was strongly associated with ACE genotype: mean LV mass altered by +2.0, +38.5, and +42.3 g in II, ID and DD, respectively (P<.0001). The prevalence of electrocardiographically defined LVH rose significantly only among those of DD genotype (from 6 of 24 before training to 11 of 24 after training, P<.01). Plasma brain natriuretic peptide levels rose by 56.0 and 11.5 pg/mL for DD and II, respectively (P<.001).

CONCLUSIONS

Exercise-induced LV growth in young males is strongly associated with the ACE I/D polymorphism.

Ultrasound diagnosis of lower limb deep venous thrombosis

Venous ultrasound imaging was compared with ascending contrast venography for the diagnosis of suspected deep vein thrombosis (DVT) in the femoral, popliteal and calf vein segments of 44 limbs in 44 patients. One femoral and one calf vein segment could not be imaged (1.5% of the segments examined), but during the same period venography failed in six patients because of an inability to cannulate a swollen limb. Ultrasound imaging compared with venography as a means of diagnosing DVT showed an overall sensitivity of 95% and a specificity of 92%. The sensitivity and specificity of ultrasound imaging for the diagnosis of both femoral and popliteal vein thromboses were 100% and 97%, respectively, and for calf vein thrombosis were 85% and 83%, respectively. This study supports the recommendation that ultrasound imaging is now the investigation of choice for the diagnosis of DVT provided that the scan is performed by an experienced vascular technologist. Ultrasound imaging may also define other pathological conditions presenting in the differential diagnosis of DVT, such as superficial thrombophlebitis and Baker's cyst.