Electrocardiogram-based biometrics for user identification - Using your heartbeat as a digital key.

External biometrics such as thumbprint and facial recognition have become standard tools for securing our digital devices and protecting our data. These systems, however, are potentially prone to copying and cybercrime access. Researchers have therefore explored internal biometrics, such as the electrical patterns within an electrocardiogram (ECG). The heart's electrical signals carry sufficient distinctiveness to allow the ECG to be used as an internal biometric for user authentication and identification. Using the ECG in this way has many potential advantages and limitations. This article reviews the history of ECG biometrics and explores some of the technical and security considerations. It also explores current and future uses of the ECG as an internal biometric.

A universal, high-performance ECG signal processing engine to reduce clinical burden.

BACKGROUND: Electrocardiogram (ECG) signal conditioning is a vital step in the ECG signal processing chain that ensures effective noise removal and accurate feature extraction. OBJECTIVE: This study evaluates the performance of the FDA 510 (k) cleared HeartKey Signal Conditioning and QRS peak detection algorithms on a range of annotated public and proprietary ECG databases (HeartKey is a UK Registered Trademark of B-Secur Ltd). METHODS: Seven hundred fifty-one raw ECG files from a broad range of use cases were individually passed through the HeartKey signal processing engine. The algorithms include several advanced filtering steps to enable significant noise removal and accurate identification of the QRS complex. QRS detection statistics were generated against the annotated ECG files. RESULTS: HeartKey displayed robust performance across 14 ECG databases (seven public, seven proprietary), covering a range of healthy and unhealthy patient data, wet and dry electrode types, various lead configurations, hardware sources, and stationary/ambulatory recordings from clinical and non-clinical settings. Over the NSR, MIT-BIH, AHA, and MIT-AF public databases, average QRS Se and PPV values of 98.90% and 99.08% were achieved. Adaptable performance (Se 93.26%, PPV 90.53%) was similarly observed on the challenging NST database. Crucially, HeartKey's performance effectively translated to the dry electrode space, with an average QRS Se of 99.22% and PPV of 99.00% observed over eight dry electrode databases representing various use cases, including two challenging motion-based collection protocols. CONCLUSION: HeartKey demonstrated robust signal conditioning and QRS detection performance across the broad range of tested ECG signals. It should be emphasized that in no way have the algorithms been altered or trained to optimize performance on a given database, meaning that HeartKey is potentially a universal solution capable of maintaining a high level of performance across a broad range of clinical and everyday use cases.

Comparative study of a single lead ECG in a wearable device.

BACKGROUND: Technological advances have led to electrocardiograph (ECG) functionality becoming increasingly accessible in wearable health devices, which has the potential to vastly expand the clinician's ability to monitor, diagnose, and manage cardiac health conditions. However, achieving the high signal quality necessary to make an accurate and confident diagnosis is inherently challenging on consumer device-acquired ECGs. Effective signal conditioning is crucial to make ECG data from wearable devices clinically actionable. OBJECTIVE: This study evaluates the heart rate (HR) performance of ECG data collected on the HeartKey® Test Watch, a single lead, dry electrode wrist wearable, against data acquired on two criterion devices: the Bittium® Faros 180, a gold standard wet electrode ambulatory monitoring device, and the HeartKey Chest Module. METHODS: ECG data was simultaneously acquired on three devices during a multi-stage protocol (sitting, walking, standing) designed to reflect the motion noise of real-life scenarios. Raw ECGs from the HeartKey Test Watch and HeartKey Chest Module were processed through HeartKey software, and the accuracy of the outputted heart rate data was compared to that of the criterion device at each stage of the protocol. A beat rejection analysis was performed to provide insight into the degree of high-frequency noise present in ECGs recorded on the HeartKey Test Watch. RESULTS: Data acquired on the HeartKey Test Watch and processed by HeartKey software generated HR metrics that closely matched that of the criterion devices throughout the protocol. Bland-Altman analysis showed a mean absolute HR difference of 0.74, 1.21, 0.80 bpm during the sitting, walking, and standing stages respectively, which is within the ± 10% or ±5 bpm range required by ANSI EC13. ECG data from the HeartKey Test Watch had a higher beat rejection rate relative to the HeartKey Chest Module (8.5% vs ∼0%) due to the excessive high-frequency noise generated during the motion-based protocol. CONCLUSION: HeartKey software demonstrated highly accurate HR performance, comparable to that of the criterion Faros device, when processing challenging ECG data acquired on a single lead, dry electrode wrist wearable during both non-motion and motion-based protocols.

A study to assess a novel automated electrocardiogram technology in screening for atrial fibrillation.

INTRODUCTION: Atrial fibrillation is often asymptomatic and un-diagnosed in the community resulting in an increased risk of heart failure and stroke to those patients. We evaluated the effectiveness, tolerability, and accuracy of a novel six-channel electrocardiogram digital-health screening device, the RhythmPad, for the detection of atrial fibrillation. METHODS: Seven hundred and fifty-two participants attending the cardiology department were recruited. Two recordings were taken-a six-lead electrocardiogram using the RhythmPad device and a standard 12-lead electrocardiogram. Recorded traces were analyzed by two blinded cardiologists. The computer-generated automated diagnostic reports from both systems were also compared. Post-participation feedback was obtained from study participants using a three-part questionnaire. RESULTS: The sensitivity of the six-lead electrocardiogram compared to the 12-lead electrocardiogram, analyzed by two blinded cardiologists, for the detection of normal sinus rhythm was 95.9%, with a specificity of 97.2%. The sensitivity for the detection of atrial fibrillation using the six-lead ECG was 93.4%, with specificity 96.8%. The six-lead automated diagnostic report had a sensitivity and specificity of 97.5% and 98.6%, respectively, for correctly diagnosing normal sinus rhythm. For the correct diagnosis of atrial fibrillation, the six-lead automated diagnostic report had a sensitivity and specificity of 95.4% and 98.8%, respectively. A total of 95.4% of participants found RhythmPad to be comfortable, with only 0.5% preferring the 12-lead ECG device in comparison to six-lead ECG acquisitions. CONCLUSION: The RhythmPad digital health device and its automated diagnostic report were highly accurate in detecting atrial fibrillation when compared to a standard 12-lead electrocardiogram.

Early aeromedical transfer after acute coronary syndromes.

AIMS: To investigate the safety and efficacy of early aeromedical transfer after acute coronary syndromes (ACS). The Island of Jersey is 160 km from the UK and as no catheter laboratory facilities exist locally, patients with ACS are transferred to tertiary centres by air ambulance in the UK for further investigations. METHODS: All patients transferred to the UK for investigation after ACS in 2008 were identified retrospectively from coronary care admission records and the local flight transfer database. Data were collected on patient demographics, diagnosis, time from presentation, flight duration, accompanying personnel and in-flight complications. Significant complications were defined as death, cardiac or respiratory arrest, sustained arrhythmia requiring electrical cardioversion or the need for endotracheal intubation. RESULTS: 65 patients (mean age 61.7 years; 80.0% male) were transferred for cardiac catheterisation after non-ST elevation myocardial infarction (n=30, 46.2%) or ST elevation myocardial infarction (n=23, 35.4%), or with unstable angina (n=12, 18.5%). Patients were transferred 3.6 ± 3.4 days after presentation; mean transfer time was 171.6 ± 38.8 min. The majority (90.8%) of patients were transferred with both a doctor and a nurse. There were no significant complications during transfer. Intra-transport medication with nitrates, diuretics, analgesia, antiemetics or antiarrhythmics was required in 15 (23.1%) patients. CONCLUSIONS: Aeromedical transfer after ACS is safe within 3 days of presentation. Given the minor nature of in-flight complications, a paramedic and coronary care nurse are sufficient medical escort for these patients.

Delayed presentation of right ventricular lead perforation following defibrillator implantation: a case report.

BACKGROUND: Perforation of a device lead through the myocardium is a recognized complication of cardiac device implantation. The associated morbidity and mortality are significant, even though it is a relatively rare complication. Therefore, it is vital for acute clinicians to be aware of the diagnosis and subsequent management of myocardial perforation. CASE SUMMARY: We present the case of a 48-year-old woman who presented to the emergency department 1 month following implantable cardioverter-defibrillator implantation with chest and shoulder pain. Initial assessment revealed bilateral pleural effusions and anaemia. Computerized tomography of her chest and abdomen demonstrated a pericardial effusion, but it was transthoracic echocardiography that confirmed the diagnosis of right ventricular perforation. Urgent system revision was undertaken. DISCUSSION: This case highlights the importance of clinical suspicion and the use of diagnostic echocardiography as an important diagnostic tool in symptomatic patient's post-cardiac device implantation.

Ventricular septal rupture following abciximab infusion.

Ventricular septal rupture is a rare complication of myocardial infarction. Despite a significant reduction in its incidence with reperfusion therapy, thrombolysis has been implicated in the pathogenesis of septal rupture. There is little information regarding the impact of glycoprotein IIb-IIIa receptor blockers on ventricular septal rupture. We report a case of rupture of the ventricular septum occurring after treatment with the glycoprotein IIb-IIIa receptor blocker abciximab, in the absence of thrombolysis.

Percutaneous closure of an iatrogenic atrial septal defect.

We report the successful percutaneous closure of an iatrogenic atrial septal defect in a 71-year-old woman. The patient had undergone mitral valve replacement and coronary artery bypass grafting, followed by redo surgery to repair a para-valvular mitral leak. Post-operatively she remained significantly limited by dyspnoea. Repeat transoesophageal echocardiography documented a large iatrogenic atrial septal defect. The patient underwent percutaneous, trans-femoral closure of the defect using the Helex septal occluder (W.L. Gore, Newark, Delaware, USA) with dramatic clinical improvement.

Biomarker Assays for Personalised Stroke Risk Assessment in Atrial Fibrillation.

BACKGROUND: Atrial fibrillation is a well-known independent risk factor for stroke yet there is no international consensus on guidelines regarding the introduction of anticoagulation in patients deemed at intermediate risk (e.g. CHA2DS2-VASc of 1). The evolution of cardiac biomarkers such as highly sensitive troponins and B-type natriuretic peptide as well as data on D-dimers, may offer incremental enhancements for personalized thromboembolism risk assessment. These markers provide prognostic data for risk of cardiovascular morbidities associated with atrial fibrillation and offer additional specificity for assessing stroke and thromboembolic risk. These assays may therefore enhance risk prognosis in atrial fibrillation alongside conventional stroke risk stratification tool patients. We seek to explore the application of personalised risk assessment using the biomarkers to aid the clinician treating the patient with atrial fibrillation deemed to be at intermediate risk of stroke. CONCLUSION: The stroke risk assessment of a patient with an intermediate risk of stroke (CHA2DS2- VASc score 1) may be improved by using cardiac biomarkers such as highly sensitive troponin, BNP and D-dimers. We explore the application of these biomarkers to provide personalised risk assessment to help a patient with AF decide on whether to commence anticoagulation.

Pharmacological management of no reflow during percutaneous coronary intervention.

Angiographic no reflow is a recognized phenomenon during percutaneous coronary intervention (PCI). It usually follows successful lesion dilation and, by definition, it represents a reduction in epicardial coronary blood flow in the absence of identifiable dissection, obstruction or distal vessel cut off (indicative of distal embolisation). No reflow appears to be more commonly associated with PCI for acute myocardial infarction and PCI for saphenous vein graft occlusions. While the exact mechanism of no reflow is unknown, theoretical causes include local humoral and microembolic effects leading to microcirculatory dysfunction. As the process is multifactorial, various therapeutic strategies are required in different situations. The present day pharmacological management involves the use of vasodilators including nitrates, verapamil, papaverine, adenosine, nicardipine and sodium nitroprusside, but interestingly a vasoconstrictor like epinephrine may also have a role. Glycoprotein IIb/IIIa platelet receptors antagonist have shown a powerful de-thrombotic effect, and the intracoronary administration appears to be particularly promising. We review the pathogenesis of a reduced epicardial flow during PCI and focus on those drugs that have been studied for the treatment of no reflow. Although no double blind, randomized trial has been conducted to assess any of these agents, or to determine the appropriate dosage, we try to identify some useful conclusions from the published evidence.

Permanent catheter drainage system for palliation of diuretic-resistant cardiac ascites.

We report the case of a 69-year-old man with dilated cardiomyopathy treated with a permanent catheter drainage system for diuretic resistant cardiac ascites. At 1 year follow-up, the patient had no heart failure related hospitalisations, displayed improved quality of life measures and had incurred no complications related to the catheter. Permanent tunnelled catheters are widely used to treat malignant ascites but may also be considered for palliation of cardiac ascites.

Is there a role for a local inpatient CT coronary angiography service in selected patients with acute coronary syndrome? A cohort analysis of inpatient tertiary centre referrals for invasive coronary angiography.

OBJECTIVE: To conduct a retrospective analysis of inpatients referred for invasive coronary angiography (ICA) at a tertiary centre, with suspected or confirmed acute coronary syndrome (ACS). METHODS: A retrospective cohort study was conducted at Jersey General Hospital. We evaluated 198 inpatients referred for ICA with suspected or confirmed ACS over a 3-year period. Patients presenting with ST elevation myocardial infarction were excluded. The primary outcome was to identify the number of patients who did not require subsequent coronary intervention following ICA. Patient variables were measured to establish those who met European Society of Cardiology (ESC) criteria for consideration of CT coronary angiography (CTCA) as an alternative to ICA. Cost of care for those referred for ICA was calculated. RESULTS: ICA demonstrated evidence of coronary heart disease requiring coronary intervention in 119 (60%) of the referred patients. 28 (35%) of the patients not requiring coronary intervention at ICA met ESC criteria for preassessment with CTCA. The cost of care for this subgroup was £9089 per patient. Inpatient CTCA was calculated at £376 per patient. CONCLUSIONS: Low-intermediate risk patients presenting with suspected or confirmed ACS to hospitals without onsite coronary revascularisation should be considered for in-hospital CTCA before consideration of ICA. Using CTCA as a gatekeeper for targeted ICA appears cost-effective, particularly for hospitals without the required onsite facilities.

Safety of contrast dobutamine stress echocardiography: a single center experience.

BACKGROUND: Contrast is increasingly being used during dobutamine stress echocardiography. However, there are few data regarding the safety of this combination. METHODS: We retrospectively analyzed 751 consecutive stress echocardiograms, 332 without contrast and 419 with contrast (299 with Sonouve, 120 with Optison). Reported side effects and physiologic data were then compared. RESULTS: There were no fatalities. The incidence of side effects was similar in the 3 groups. The Optison group had a lower diastolic blood pressure compared with the noncontrast group ( P < .05) at rest, and the Sonovue group had a higher peak heart rate compared with the noncontrast group ( P < .001). Patients receiving Optison had more premature atrial contractions ( P < .05) but there was no difference in the incidence of ventricular tachycardia, supraventricular tachycardia, or vagally mediated episodes. CONCLUSION: The use of contrast during dobutamine stress echocardiography was not associated with an increased risk of side effects.

Percutaneous treatment of simultaneous aortic dissection and pericardial tamponade during coronary intervention.

We report on a case of an unexpected dissection of the left main stem during percutaneous coronary intervention complicated by involvement of the ascending aorta with pericardial tamponade. After pericardial drainage, haemodynamic stabilization, and extensive stenting of the propagating dissection, safe discharge was possible without surgical intervention.

What is the role of balloon dilatation for severe aortic stenosis during pregnancy?

BACKGROUND AND AIM OF THE STUDY: Severe aortic stenosis in pregnancy creates several challenges for the physician. In recent years, balloon valvuloplasty has become more widely used, though the indications for its use in this setting are unclear. A review of the available evidence is presented, and a suggested management strategy illustrated. METHODS AND RESULTS: Available literature on the subject was reviewed via Medline search and reference lists from the identified articles. Particular attention was paid to prediction of risk, management options and outcome. The data suggest the importance of early symptoms in determining management, as there is a high risk of complications if left untreated. This group should be considered for valvuloplasty, whereas asymptomatic patients are at low risk, and can be managed expectantly. This is illustrated with two contrasting cases from the authors' practice: the symptomatic patient underwent aortic balloon valvuloplasty as a palliative procedure, using transesophageal and minimal fluoroscopic guidance, with good medium-term results. Both patients required aortic valve replacement in the medium to long-term. CONCLUSION: The use of aortic balloon valvuloplasty in pregnancy is useful as a palliative procedure, allowing deferral of valve replacement until after birth. Echocardiographic features alone are not enough to decide on management, and symptoms play a vital role in determining risk. The use of transesophageal echocardiography during the procedure significantly reduces fluoroscopy time.

Flecainide overdose--support using an intra-aortic balloon pump.

BACKGROUND: Flecainide is an antiarrhythmic agent which is being used increasingly for the management of super-ventricular arrhythmias. Overdose with flecainide is frequently fatal with mortality reported as high as 22% due to arrhythmias, myocardial depression and conduction defects leading to electro-mechanical dissociation and asytole. Supportive measures are often required during the case and previously have included inotropes, extracorporeal membrane oxygenation and cardiopulmonary bypass. CASE PRESENTATION: A 47 year old lady presented to the emergency department with a four hour history of severe central chest pain. Her ECG showed atrial fibrillation and broad QRS complexes with a sine wave appearance. She had a past history of paroxysmal atrial fibrillation and significant psychiatric history. Following thrombolysis for a presumed myocardial infarction she developed cardiogenic shock with severely impaired left ventricular function. An intra-aortic balloon pump was inserted and coronary angiography demonstrated normal coronary arteries. With inotropic support she improved over 48 hours, with both her QRS duration and left ventricular function returning to normal. Biochemical testing following her discharge demonstrated significantly elevated levels of flecainide. CONCLUSION: The use of an intra-aortic balloon pump is a useful supportive measure during the acute phase of flecainide overdose associated with severe myocardial depression.

Improving the acceptability of the atrial defibrillator for the treatment of persistent atrial fibrillation: the atrial defibrillator sedation assessment study (ADSAS).

BACKGROUND: To compare the acceptability and effectiveness of three pre-medication regimens for manually activated cardioversion of recurrent persistent atrial fibrillation. METHODS: Eighteen patients implanted with the Jewel AF atrial defibrillator for drug-resistant persistent atrial fibrillation only were studied in an open-labelled randomised crossover study. Patients were assigned to sedation (S) with midazolam elixir, analgesia (A) with morphine sulphate or combination therapy (C) with dextromoramide and lorazepam. Pre-medication was taken up to 1 h before cardioversion. Patients rotated through each type of medication after undertaking at least one cardioversion. Visual analogue scales were completed immediately post-cardioversion and 24 h later for pain, anxiety and 'unpleasantness'. Higher scores represented a worse outcome. RESULTS: After 2 years' follow-up, 238 cardioversions were performed with S, 17 with A and 35 with C. The mean immediate combined score for S (10.9, 95% confidence interval (CI) 8.2-13.6) was significantly lower than for A (17.3, 95% CI 15.1-19.5, P = 0.01) and for C (15.9, 95% CI 12.3-19.6, P = 0.02). All patients who used S chose it as the most favourable pre-medicant. All patients who used A found it the least acceptable. CONCLUSION: Sedation rather than analgesia enhanced the acceptability of manually activated atrial defibrillation.