Feasibility of combining serial smartphone single-lead electrocardiograms for the diagnosis of ST-elevation myocardial infarction.

BACKGROUND: The rate-limiting step in STEMI diagnosis often is the availability of a 12-lead electrocardiogram (ECG) and its interpretation. The potential may exist to speed the availability of 12-lead ECG information by using commonly available mobile technologies. We sought to test whether combining serial smartphone single-lead ECGs to create a virtual 12-lead ECG can accurately diagnose STEMI. METHODS: Consenting patients presenting with symptoms consistent with a possible STEMI had contemporaneous standard 12-lead and smartphone '12-lead equivalent' ECG (produced by electronically combining serial single-lead ECGs) recordings obtained. Matched ECGs were evaluated qualitatively and quantitatively by a panel of blinded readers and classified as STEMI/STEMI equivalent (LBBB), Not-STEMI, or uninterpretable. Interpretable ECG pairs were graded as showing good, fair, or poor correlation. RESULTS: Two hundred four subjects (age = 60 years, males = 57%, STEMI activation = 45%) were enrolled from 5 international sites. Smartphone ECG quality was graded as good in 151 (74.0%), fair in 32 (15.7%), poor in 8 (3.9%), and uninterpretable in 13 (6.4%). A STEMI/STEMI equivalent diagnosis was identified by standard 12-lead ECG in 57/204 (27.9%) recordings. For all interpretable pairs of smartphone ECGs compared with standard ECGs (n = 190), the sensitivity, specificity, and positive and negative predictive values for STEMI/STEMI equivalent by smartphone were 0.89, 0.84, 0.70 and 0.95, respectively. CONCLUSIONS: A '12-lead equivalent' ECG obtained from multiple serial single-lead ECGs from a smartphone can identify STEMI with good correlation to a standard 12-lead ECG. This technology holds promise to improve outcomes in STEMI by enhancing the reach and speed of diagnosis and thereby early treatment.

Association of the dispersion in red blood cell volume with mortality.

BACKGROUND: The red cell distribution width (RDW) predicts mortality among many populations. RDW is calculated as the standard deviation (SD) of the red blood cell (RBC) volume divided by mean corpuscular volume (MCV). Because higher MCV also predicts mortality, we hypothesized that the RDW numerator (one SD of RBC volume or 1SD-RDW) predicts mortality more strongly than the RDW. MATERIAL AND METHODS: Adult subjects hospitalized during a contemporary clinical era (10/2005-1/2014, N = 135,963) and a historical era (1/1999-9/2005, N = 119,530) were studied. The RDW was obtained from the complete blood count (CBC), while 1SD-RDW was calculated (RDW multiplied by MCV and divided by 100). RESULTS: In univariable Cox regression (2005-2014 cohort), 1SD-RDW (quintile 5 vs. 1: hazard ratio [HR] = 8.38, 95% confidence interval [CI] = 7.94, 8.85; P < 0.001) was a superior predictor of mortality compared to RDW (quintile 5 vs. 1: HR = 4.78, CI = 4.57, 5.00; P < 0.001). This superiority remained after adjustment for age, sex, basic metabolic profile components and other CBC factors excluding MCV (1SD-RDW: HR = 2.41, CI = 2.28, 2.55; RDW: HR = 2.01, CI = 1.92, 2.11). Further adjustment for MCV strengthened the RDW association (HR = 2.14, CI = 2.04, 2.24; P < 0.001), becoming indistinct from 1SD-RDW (HR = 2.20, CI = 2.08, 2.33; P < 0.001). Findings were similar for the 1999-2005 cohort. CONCLUSIONS: The 1SD-RDW predicted mortality more strongly than RDW, suggesting that 1SD-RDW is superior to RDW as an individual risk predictor. Further, these results indicate that the dispersion of RBC volume and its mean are independent risk markers. Further research is required to understand the clinical value and mechanistic basis of these associations.

Smartphone ECG for evaluation of STEMI: results of the ST LEUIS Pilot Study.

BACKGROUND: 12-lead ECG is a critical component of initial evaluation of cardiac ischemia, but has traditionally been limited to large, dedicated equipment in medical care environments. Smartphones provide a potential alternative platform for the extension of ECG to new care settings and to improve timeliness of care. OBJECTIVE: To gain experience with smartphone electrocardiography prior to designing a larger multicenter study evaluating standard 12-lead ECG compared to smartphone ECG. METHODS: 6 patients for whom the hospital STEMI protocol was activated were evaluated with traditional 12-lead ECG followed immediately by a smartphone ECG using right (VnR) and left (VnL) limb leads for precordial grounding. The AliveCor™ Heart Monitor was utilized for this study. All tracings were taken prior to catheterization or immediately after revascularization while still in the catheterization laboratory. RESULTS: The smartphone ECG had excellent correlation with the gold standard 12-lead ECG in all patients. Four out of six tracings were judged to meet STEMI criteria on both modalities as determined by three experienced cardiologists, and in the remaining two, consensus indicated a non-STEMI ECG diagnosis. No significant difference was noted between VnR and VnL. CONCLUSIONS: Smartphone based electrocardiography is a promising, developing technology intended to increase availability and speed of electrocardiographic evaluation. This study confirmed the potential of a smartphone ECG for evaluation of acute ischemia and the feasibility of studying this technology further to define the diagnostic accuracy, limitations and appropriate use of this new technology.

Successful avoidance of superior vena cava injury during transvenous lead extraction using a tandem femoral-superior approach.

BACKGROUND: Transvenous pacemaker and defibrillator lead extraction is a higher risk procedure with variation in preferred technique. A frequently fatal complication of this procedure is perforation of the superior vena cava. We have developed a tandem femoral-superior technique that incorporates snaring of targeted leads from a femoral approach combined with use of a rotational cutting sheath advanced over the lead from the subclavian vein. OBJECTIVE: We sought to evaluate the safety and efficacy of a tandem femoral-superior approach to lead extraction. METHODS: Consecutive patients undergoing transvenous extraction of at least 1 pacemaker or defibrillator lead with implant duration ≥1 year in which a tandem femoral-superior technique was used as the initial extraction strategy were included. The registry spanned 2010-2018 and consisted of procedures performed by a single primary operator. RESULTS: A total of 131 patients were included. A total of 267 leads with a mean implant duration of 9.8 years, including 90 defibrillator leads (33.7%), were targeted for extraction. No superior vena cava perforation or other vascular damage occurred. Clinical procedural success was achieved in 96.2% of cases. There were 5 major complications (3.8% of patients), with 3 being pericardial effusion requiring intervention. There were no deaths. CONCLUSION: A tandem femoral-superior approach to lead extraction effectively eliminated superior vena cava injury. This is a safe and effective technique for transvenous lead extraction.

Extreme erythrocyte macrocytic and microcytic percentages are highly predictive of morbidity and mortality.

BACKGROUND: The red cell distribution width (RDW) is associated with health outcomes. Whether non-RDW risk information is contained in RBC sizes is unknown. This study evaluated the association of the percentage of extreme macrocytic RBCs (%Macro, RBC volume > 120 fl) and microcytic RBCs (%Micro, RBC volume < 60 fl) and the RDW-size distribution (RDW-sd) with mortality and morbidity. METHODS: Patients (females, n = 165,770; males, n = 100,210) at Intermountain Healthcare were studied if they had a hematology panel between May 2014 and September 2016. Adjusted sex-specific associations of %Macro/%Micro and RDW-sd with mortality and 33 morbidities were evaluated. RESULTS: Among females with fourth-quartile values of %Macro quartile and %Micro (referred to throughout as 4/4), there was an average of 7.2 morbidities versus 2.9 in the lowest risk (LR1) categories, 1/1, 1/2, 2/1, and 2/2 (P < 0.001). Among males, those in the 4/4 category had 8.0 morbidities, while those in the LR1 had 3.4 (P < 0.001). Cox regressions found %Macro/%Micro (4/4 vs. LR1, females: hazard ratio [HR] = 1.97 [95% CI = 1.53, 2.54]; males: HR = 2.17 [CI = 1.72, 2.73]), RDW-sd (quartile 4 vs. 1, females: HR = 1.33 [CI = 1.04, 1.69]; males: HR = 1.41 [CI = 1.10, 1.80]), and RDW (quartile 4 vs. 1, females: HR = 1.59 [CI = 1.26, 2.00]; males: HR = 1.23 [CI = 0.99, 1.52]) independently predicted mortality. Limitations include that the observational design did not reveal causality and unknown confounders may be unmeasured. CONCLUSIONS: Concomitantly elevated %Macro and %Micro predicted the highest mortality risk and the greatest number of morbidities, revealing predictive ability of RBC volume beyond what is measured clinically. Mechanistic investigations are needed to explain the biological basis of these observations. FUNDING: This study was supported by internal Intermountain Heart Institute funds and in-kind support from Sysmex America Inc.