Breaking Bias: The Role of Artificial Intelligence in Improving Clinical Decision-Making.

This case report reflects on a delayed diagnosis for a 27-year-old woman who reported chest pain and shortness of breath to the emergency department. The treating clinician reflects upon how cognitive biases influenced their diagnostic process and how multiple missed opportunities resulted in missteps. Using artificial intelligence (AI) tools for clinical decision-making, we suggest how AI could augment the clinician, and in this case, delayed diagnosis avoided. Incorporating AI tools into clinical decision-making brings potential benefits, including improved diagnostic accuracy and addressing human factors contributing to medical errors. For example, they may support a real-time interpretation of medical imaging and assist clinicians in generating a differential diagnosis in ensuring that critical diagnoses are considered. However, it is vital to be aware of the potential pitfalls associated with the use of AI, such as automation bias, input data quality issues, limited clinician training in interpreting AI methods, and the legal and ethical considerations associated with their use. The report draws attention to the utility of AI clinical decision-support tools in overcoming human cognitive biases. It also emphasizes the importance of clinicians developing skills needed to steward the adoption of AI tools in healthcare and serve as patient advocates, ensuring safe and effective use of health data.

Five-Year Outcomes after PCI or CABG for Left Main Coronary Disease.

BACKGROUND: Long-term outcomes after percutaneous coronary intervention (PCI) with contemporary drug-eluting stents, as compared with coronary-artery bypass grafting (CABG), in patients with left main coronary artery disease are not clearly established. METHODS: We randomly assigned 1905 patients with left main coronary artery disease of low or intermediate anatomical complexity (according to assessment at the participating centers) to undergo either PCI with fluoropolymer-based cobalt-chromium everolimus-eluting stents (PCI group, 948 patients) or CABG (CABG group, 957 patients). The primary outcome was a composite of death, stroke, or myocardial infarction. RESULTS: At 5 years, a primary outcome event had occurred in 22.0% of the patients in the PCI group and in 19.2% of the patients in the CABG group (difference, 2.8 percentage points; 95% confidence interval [CI], -0.9 to 6.5; P = 0.13). Death from any cause occurred more frequently in the PCI group than in the CABG group (in 13.0% vs. 9.9%; difference, 3.1 percentage points; 95% CI, 0.2 to 6.1). In the PCI and CABG groups, the incidences of definite cardiovascular death (5.0% and 4.5%, respectively; difference, 0.5 percentage points; 95% CI, -1.4 to 2.5) and myocardial infarction (10.6% and 9.1%; difference, 1.4 percentage points; 95% CI, -1.3 to 4.2) were not significantly different. All cerebrovascular events were less frequent after PCI than after CABG (3.3% vs. 5.2%; difference, -1.9 percentage points; 95% CI, -3.8 to 0), although the incidence of stroke was not significantly different between the two groups (2.9% and 3.7%; difference, -0.8 percentage points; 95% CI, -2.4 to 0.9). Ischemia-driven revascularization was more frequent after PCI than after CABG (16.9% vs. 10.0%; difference, 6.9 percentage points; 95% CI, 3.7 to 10.0). CONCLUSIONS: In patients with left main coronary artery disease of low or intermediate anatomical complexity, there was no significant difference between PCI and CABG with respect to the rate of the composite outcome of death, stroke, or myocardial infarction at 5 years. (Funded by Abbott Vascular; EXCEL ClinicalTrials.gov number, NCT01205776.).

New-Onset Atrial Fibrillation After PCI or CABG for Left Main Disease: The EXCEL Trial.

BACKGROUND: There is limited information on the incidence and prognostic impact of new-onset atrial fibrillation (NOAF) following percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) for left main coronary artery disease (LMCAD). OBJECTIVES: This study sought to determine the incidence of NOAF following PCI and CABG for LMCAD and its effect on 3-year cardiovascular outcomes. METHODS: In the EXCEL (Evaluation of XIENCE Versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization) trial, 1,905 patients with LMCAD and low or intermediate SYNTAX scores were randomized to PCI with everolimus-eluting stents versus CABG. Outcomes were analyzed according to the development of NOAF during the initial hospitalization following revascularization. RESULTS: Among 1,812 patients without atrial fibrillation on presentation, NOAF developed at a mean of 2.7 ± 2.5 days after revascularization in 162 patients (8.9%), including 161 of 893 (18.0%) CABG-treated patients and 1 of 919 (0.1%) PCI-treated patients (p < 0.0001). Older age, greater body mass index, and reduced left ventricular ejection fraction were independent predictors of NOAF in patients undergoing CABG. Patients with versus without NOAF had a significantly longer duration of hospitalization, were more likely to be discharged on anticoagulant therapy, and had an increased 30-day rate of Thrombolysis In Myocardial Infarction major or minor bleeding (14.2% vs. 5.5%; p < 0.0001). By multivariable analysis, NOAF after CABG was an independent predictor of 3-year stroke (6.6% vs. 2.4%; adjusted hazard ratio [HR]: 4.19; 95% confidence interval [CI]: 1.74 to 10.11; p = 0.001), death (11.4% vs. 4.3%; adjusted HR: 3.02; 95% CI: 1.60 to 5.70; p = 0.0006), and the primary composite endpoint of death, MI, or stroke (22.6% vs. 12.8%; adjusted HR: 2.13; 95% CI: 1.39 to 3.25; p = 0.0004). CONCLUSIONS: In patients with LMCAD undergoing revascularization in the EXCEL trial, NOAF was common after CABG but extremely rare after PCI. The development of NOAF was strongly associated with subsequent death and stroke in CABG-treated patients. Further studies are warranted to determine whether prophylactic strategies to prevent or treat atrial fibrillation may improve prognosis in patients with LMCAD who are undergoing CABG. (Evaluation of XIENCE Versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization [EXCEL]; NCT01205776).

Transvenous Lead Extraction in Adults With Congenital Heart Disease: Insights From a 20-Year Single-Center Experience.

BACKGROUND: Safety and feasibility data on transvenous lead extraction (TLE) in the challenging population of adults with congenital heart disease (A-CHD) are limited. Herein, we report the results of TLE in A-CHD during a 20-year period. METHODS AND RESULTS: All consecutive TLE procedures in A-CHD were included in a monocentric prospective registry from 1996. A total of 121 leads were extracted in 49 A-CHD (median age, 38 years; 51% men) during 71 TLE procedures. Twenty-four (49%) patients had transposition of the great arteries. Main indications for extraction were infection in 34 (48%) and lead failure in 22 (31%). A laser sheath was required for 56 (46%) leads and a femoral approach for 10 (8%). Complete TLE was achieved for 111 leads (92%). In multivariable analysis, lead duration (odds ratio, 1.02; 95% confidence interval, 1.00-1.04; P<0.01) and number of previous cardiac surgeries (odds ratio, 2.65; 95% confidence interval, 1.52-4.67; P<0.01) were predictive of TLE failure. No perioperative death or pericardial effusion was observed. Subpulmonary atrioventricular valve regurgitation increased in 8 patients (5 with transposition of the great arteries) and was independently associated with an implantable cardioverter defibrillator lead (odds ratio, 9.69; 95% confidence interval, 1.31-71.64; P=0.03) and valvular vegetation (odds ratio, 7.29; 95% confidence interval, 1.32-40.51; P=0.02). After a median of 54 (19-134) months of follow-up after the first TLE, 3 deaths occurred independently from lead management. CONCLUSIONS: Despite complex anatomic issues, TLE can be achieved successfully in most A-CHD using advanced extraction techniques. Subpulmonary atrioventricular valve regurgitation is a prevalent complication, particularly in patients with transposition of the great arteries.

Differences and similarities in risk factors for postoperative acute kidney injury between younger and older adults undergoing cardiac surgery.

OBJECTIVES: Acute kidney injury is a frequent complication after cardiac surgery. The purpose of this study was to assess the risk factors for acute kidney injury in patients ≤60 years of age undergoing cardiac surgery and to compare these risk factors with those identified in patients ≥65 years of age. METHODS: From 2010 to 2012, 1253 patients ≤60 years (mean age 52 ± 9 years) and 2488 patients ≥65 years (mean age 74 ± 6 years) underwent cardiac surgery. Linear regression models using least absolute shrinkage and selection operator methods and mixed effects linear regression models were used to assess factors associated with maximum postoperative increase in serum creatinine in these two cohorts. RESULTS: In both age groups, the following variables were associated independently with greater degrees of postoperative increase in serum creatinine on multivariable analysis: greater body mass index, peripheral vascular disease, preoperative use of diuretics, lower preoperative hemoglobin, preoperative intra-aortic balloon pump, urgent or emergent status, long cardiopulmonary bypass time, and hemofiltration. In younger patients, a greater increase in serum creatinine was associated with diabetes, and previous cardiac surgery, whereas female sex was associated with a lower degree of increase in serum creatinine. In older patients, a greater increase in serum creatinine was associated with age, hypertension, smoking, and lower left ventricular left ejection fraction. Operation type and coronary artery disease had a different impact on postoperative creatinine increase between younger and older patients. CONCLUSIONS: This study identified both common and distinct risk factors associated with postoperative increase in serum creatinine between patients ≤60 years and those ≥65 years undergoing cardiac surgery. Importantly, all potentially modifiable risk factors were present in both groups.

Everolimus-Eluting Stents or Bypass Surgery for Left Main Coronary Artery Disease.

BACKGROUND: Patients with obstructive left main coronary artery disease are usually treated with coronary-artery bypass grafting (CABG). Randomized trials have suggested that drug-eluting stents may be an acceptable alternative to CABG in selected patients with left main coronary disease. METHODS: We randomly assigned 1905 eligible patients with left main coronary artery disease of low or intermediate anatomical complexity to undergo either percutaneous coronary intervention (PCI) with fluoropolymer-based cobalt-chromium everolimus-eluting stents (PCI group, 948 patients) or CABG (CABG group, 957 patients). Anatomic complexity was assessed at the sites and defined by a Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery (SYNTAX) score of 32 or lower (the SYNTAX score reflects a comprehensive angiographic assessment of the coronary vasculature, with 0 as the lowest score and higher scores [no upper limit] indicating more complex coronary anatomy). The primary end point was the rate of a composite of death from any cause, stroke, or myocardial infarction at 3 years, and the trial was powered for noninferiority testing of the primary end point (noninferiority margin, 4.2 percentage points). Major secondary end points included the rate of a composite of death from any cause, stroke, or myocardial infarction at 30 days and the rate of a composite of death, stroke, myocardial infarction, or ischemia-driven revascularization at 3 years. Event rates were based on Kaplan-Meier estimates in time-to-first-event analyses. RESULTS: At 3 years, a primary end-point event had occurred in 15.4% of the patients in the PCI group and in 14.7% of the patients in the CABG group (difference, 0.7 percentage points; upper 97.5% confidence limit, 4.0 percentage points; P=0.02 for noninferiority; hazard ratio, 1.00; 95% confidence interval, 0.79 to 1.26; P=0.98 for superiority). The secondary end-point event of death, stroke, or myocardial infarction at 30 days occurred in 4.9% of the patients in the PCI group and in 7.9% in the CABG group (P<0.001 for noninferiority, P=0.008 for superiority). The secondary end-point event of death, stroke, myocardial infarction, or ischemia-driven revascularization at 3 years occurred in 23.1% of the patients in the PCI group and in 19.1% in the CABG group (P=0.01 for noninferiority, P=0.10 for superiority). CONCLUSIONS: In patients with left main coronary artery disease and low or intermediate SYNTAX scores by site assessment, PCI with everolimus-eluting stents was noninferior to CABG with respect to the rate of the composite end point of death, stroke, or myocardial infarction at 3 years. (Funded by Abbott Vascular; EXCEL ClinicalTrials.gov number, NCT01205776 .).

Brain Natriuretic Peptide Levels and the Occurrence of Subclinical Pulmonary Edema in Healthy Lowlanders at High Altitude.

BACKGROUND: High altitude (HA) pulmonary edema (PE) results from complex and misunderstood interactions between adaptation mechanisms. We assessed the occurrence of subclinical PE and brain natriuretic peptide (BNP) levels among nonacclimatized individuals during an expedition on Mount Elbrus (5642 m). METHODS: Seven subjects underwent assessment of vital signs, Lake Louise Score, ultrasound lung comets using handheld echography and circulating BNP using capillary testing at different stages of ascension, in addition to baseline echocardiography. Friedman tests were used to compare serial measurements. RESULTS: Heart rate, Lake Louise Score (P < 0.0001) and blood pressure (P = 0.037) increased during ascension; oxygen saturation decreased (P < 0.0001). BNP increased (40.7 ± 16.8 vs 19.7 ± 3.04 pg/mL; P < 0.01) after the summit, as did ultrasound lung comet count throughout ascension (P < 0.0001), but both parameters were not correlated (r = 0.36; P = 0.42). Post-summit peak BNP correlated with baseline left ventricular mass index (r = -0.79; P = 0.033). CONCLUSION: This study confirms the high incidence of subclinical PE during subacute exposure to hypobaric hypoxia and enhancement of this phenomenon after exertion. Although not correlated with the degree of PE, BNP levels increased after sustained effort at HA, but not at rest. Further investigation is needed to determine the mechanisms underlying the BNP response at HA and its usefulness as a monitoring tool during expeditions.

Right Ventricular Depression After Cardiopulmonary Bypass for Valvular Surgery.

OBJECTIVE: To assess if right ventricular (RV) dysfunction is associated with increased mortality after cardiac surgery. DESIGN: Post-hoc analysis of a single-center double-blind randomized controlled trial. SETTING: University hospital. PARTICIPANTS: A total of 120 patients undergoing simple or complex valvular surgery. INTERVENTIONS: Patients were randomized to receive intravenous amiodarone or placebo intraoperatively. As secondary analysis, patients were divided into those requiring or not requiring postoperative inotropic agents. MEASUREMENTS AND MAIN RESULTS: After cardiopulmonary bypass (CPB), there were significant increases in heart rate, cardiac index, systolic and mean arterial pressures, central venous pressure and pulmonary capillary wedge pressure with reduction in systemic vascular resistance (p<0.05). Right ventricular end-systolic area became larger in those without inotropes and tricuspid annular plane systolic excursion was reduced in all patients; mitral annular systolic velocities were higher in patients receiving inotropes. Both right- and left-sided Doppler signals were altered significantly after CPB, which may be attributed to increased filling pressure. Inotropic agents were required in 56 patients after CPB (47%). The use of inotropic agents was associated with increased left and right atrial velocities (p<0.05). There were no differences in postoperative complications between groups; however, the number of deaths at 6 years was increased in patients who received inotropes after CPB (p = 0.0247). CONCLUSIONS: The increases in right-sided dimensions after CPB are associated with reduction in RV function and increased biventricular filling pressure, suggesting worsening biventricular function and interventricular dependence. Inotropic medications were associated with unaltered RV dimensions and increased biatrial activity.

Biatrial neuroablation attenuates atrial remodeling and vulnerability to atrial fibrillation in canine chronic rapid atrial pacing.

AIMS: We investigated the proposition that an intact cardiac nervous system may contribute to electrophysiological remodeling and increased vulnerability to atrial fibrillation (AF) following chronic rapid atrial pacing (RAP). METHODS AND RESULTS: Baseline study was conducted prior to ablating right and left ganglionated plexuses (RAGP, LAGP) in 11 anesthetized canines (Neuroablation group) and in 11 canines without neuroablation (Intact GP). After being subjected to RAP (400 beats/min) for 6 weeks, animals were reanesthetized for terminal study. The ERP shortening typical of chronic RAP was significantly more pronounced in the Intact GP (baseline: 112 ± 12 to terminal: 80 ± 11 ms) than in the Neuroablation group (113 ± 18 to 102 ± 21 ms, p < .001), and AF inducibility (extrastimulus protocol) showed significantly greater increment in the Intact GP (baseline: 23 ± 19% to terminal: 60 ± 17% of trials) than in the Neuroablation group (18 ± 15% to 27 ± 17%, p = 0.029). Negative chronotropic responses to right vagus nerve stimulation were markedly reduced immediately after the neuroablation procedure but had recovered at terminal study. Vagally-evoked repolarization changes (from 191 unipolar electrograms) occurred in a majority of Intact GP animals in the superior, middle and inferior RA free wall, and in the LA appendage. In the Neuroablation group, repolarization changes were restricted to the superior RA free wall but none occurred in the inferior RA and only infrequently in the LA appendage, yielding significantly smaller affected areas in Neuroablation than in Intact GP animals. CONCLUSION: Persistent functional denervation in LA and RA regions other than RA pacemaker areas may contribute to prevent the development of a tachycardia-dependent AF substrate.

Acute intraoperative effect of intravenous amiodarone on right ventricular function in patients undergoing valvular surgery.

BACKGROUND: Amiodarone is commonly used in the acute care setting. However the acute hemodynamic and echocardiographic effect of intravenous amiodarone administered intraoperatively on right ventricular (RV) systolic and diastolic function using transesophageal echocardiography (TEE) has not been described. METHODS: The study design was a randomized controlled trial in elective cardiac surgical patients undergoing valvular surgery. Patients received an intravenous loading dose of 300 mg of either amiodarone or placebo in the operating room, followed by an infusion of 15 mg/kg for two days. Hemodynamic profiles, echocardiographic measurement of RV and left ventricular (LV) dimensions, Doppler interrogation of tricuspid and mitral valve, hepatic and pulmonary venous flow combined with tissue Doppler imaging of the tricuspid and mitral valve annulus were obtained before and after bolus. RESULTS: Although more patients in the placebo group had chronic obstructive lung disease (14 vs 6, p=0.05) and diabetes (14 vs 5; p=0.0244), there was no difference in terms of baseline hemodynamic, 2D and Doppler variables. After bolus, a significant increase in pulmonary artery pressure, central venous pressure and pulmonary vascular resistance index (p<0.05) was observed in the amiodarone group with reduction in systolic to diastolic (S/D) ratio of the hepatic (p=0.0247) and pulmonary venous (p=0.0052) velocity. CONCLUSION: Acute administration of amiodarone is associated with alteration in RV diastolic properties and has minimal negative inotropic effect on RV systolic function in cardiac surgical patients with valvular disease.

Excellent outcomes for transcatheter aortic valve replacement within 1 year of opening a low-volume centre and consideration of requirements.

BACKGROUND: After the approval of transcatheter aortic valve replacement (TAVR) for high-risk or inoperable patients with severe aortic stenosis (AS), many low- and moderate-volume TAVR programs were initiated. Contemporary outcomes from these newly initiated centres remain unknown. METHODS: In March 2013, our institution was authorized by the Québec Ministry of Health to perform 30 TAVR procedures. After thorough clinical screening and imaging evaluation, suitable patients underwent transfemoral TAVR with the balloon-expandable SAPIEN XT (Edwards Lifesciences, Irvine, CA) transcatheter heart valve (THV). In-hospital and 30-day outcomes were prospectively collected and reported according to Valve Academic Research Consortium 2 guidelines. RESULTS: From April 2013 to January 2014, 30 consecutive high-risk (n = 16 [53.3%]) or inoperable (n = 14 [46.7%]) patients (mean age, 84.6 years; mean Society of Thoracic Surgery score, 7) with symptomatic severe AS underwent transfemoral TAVR. No catastrophic intraprocedural complications such as annulus rupture, valve embolization, aortic dissection, or coronary occlusion occurred, and there were no deaths at 30 days. Disabling stroke occurred in 1 (3.3%) patient 48 hours after THV implantation. Major vascular complications and major bleeding occurred in 1 (3.3%) patient. No moderate or severe paravalvular leak was observed. The median length of stay was 2 (1-3) days, with 8 (26.7%) patients discharged within 24 hours after the procedure. CONCLUSIONS: Excellent outcomes can be achieved in newly initiated relatively low-volume centres, which compares favorably to previously published large series. Important considerations include appropriate team training, rigorous patient screening, use of multimodality imaging techniques, a heart team approach, constant integration of lessons learned from larger published experiences, and maintaining a recommended minimum volume of 25 cases per year.

Surgical treatment of moderate ischemic mitral regurgitation.

BACKGROUND: Ischemic mitral regurgitation is associated with increased mortality and morbidity. For surgical patients with moderate regurgitation, the benefits of adding mitral-valve repair to coronary-artery bypass grafting (CABG) are uncertain. METHODS: We randomly assigned 301 patients with moderate ischemic mitral regurgitation to CABG alone or CABG plus mitral-valve repair (combined procedure). The primary end point was the left ventricular end-systolic volume index (LVESVI), a measure of left ventricular remodeling, at 1 year. This end point was assessed with the use of a Wilcoxon rank-sum test in which deaths were categorized as the lowest LVESVI rank. RESULTS: At 1 year, the mean LVESVI among surviving patients was 46.1±22.4 ml per square meter of body-surface area in the CABG-alone group and 49.6±31.5 ml per square meter in the combined-procedure group (mean change from baseline, -9.4 and -9.3 ml per square meter, respectively). The rate of death was 6.7% in the combined-procedure group and 7.3% in the CABG-alone group (hazard ratio with mitral-valve repair, 0.90; 95% confidence interval, 0.38 to 2.12; P=0.81). The rank-based assessment of LVESVI at 1 year (incorporating deaths) showed no significant between-group difference (z score, 0.50; P=0.61). The addition of mitral-valve repair was associated with a longer bypass time (P<0.001), a longer hospital stay after surgery (P=0.002), and more neurologic events (P=0.03). Moderate or severe mitral regurgitation was less common in the combined-procedure group than in the CABG-alone group (11.2% vs. 31.0%, P<0.001). There were no significant between-group differences in major adverse cardiac or cerebrovascular events, deaths, readmissions, functional status, or quality of life at 1 year. CONCLUSIONS: In patients with moderate ischemic mitral regurgitation, the addition of mitral-valve repair to CABG did not result in a higher degree of left ventricular reverse remodeling. Mitral-valve repair was associated with a reduced prevalence of moderate or severe mitral regurgitation but an increased number of untoward events. Thus, at 1 year, this trial did not show a clinically meaningful advantage of adding mitral-valve repair to CABG. Longer-term follow-up may determine whether the lower prevalence of mitral regurgitation translates into a net clinical benefit. (Funded by the National Institutes of Health and the Canadian Institutes of Health Research; ClinicalTrials.gov number, NCT00806988.).

Electrophysiological changes preceding the onset of atrial fibrillation after coronary bypass grafting surgery.

BACKGROUND: The incidence of Post-CABG atrial fibrillation (AF) lies between 25% and 40%. It worsens morbidity and raises post-operative costs. Detection of incoming AF soon enough for prophylactic intervention would be helpful. The study is to investigate the electrophysiological changes preceding the onset of AF and their relationship to the preoperative risk. METHODS AND RESULTS: Patients were recorded continuously for the first four days after coronary artery bypass grafting surgery (CABG) with three unipolar electrodes sutured to the atria (AEG). The patients experiencing an AF lasting more than 10 minutes were selected and the two hours before the onset were analyzed. Four variables were found to show significant changes in the two hours prior to the first prolonged AF: increasing rate of premature atrial activation, increasing incidence of short transient arrhythmias, acceleration of heart rate, and rise of low frequency content of heart rate. The main contrast was between the first and last hour before AF onset. Preoperative risk was not predictive of the onset time of AF and did not correlate with the amplitude of changes prior to AF. CONCLUSIONS: Post-CABG AF were preceded by electrophysiological changes occurring in the last hour before the onset of the arrhythmia, whereas none of these changes was found to occur in all AF patients. The risk was a weighted sum of factors related to the density of premature activations and the state of atrial substrate reflected by the sinus rhythm and its frequency content prior to AF. Preoperative risk score seems unhelpful in setting a detection threshold for the AF onset.

Atrial fibrillation - new frontiers in anticoagulation.

Stroke is the most feared complication of atrial fibrillation but for over fifty years there has been no simple, effective preventative alternative to warfarin. The development of new risk algorithms such as CHADSVASC has resulted in more patients being recommended anticoagulation therapy. Fixed dose oral anticoagulation is a landmark in drug development for atrial fibrillation. The differences between the drugs are discussed and the trial data examined. As we enter this new frontier of therapy, there is no doubt that these drugs will transform the delivery of anticoagulation for patients with atrial fibrillation.

Simultaneous epicardial and noncontact endocardial mapping of the canine right atrium: simulation and experiment.

Epicardial high-density electrical mapping is a well-established experimental instrument to monitor in vivo the activity of the atria in response to modulations of the autonomic nervous system in sinus rhythm. In regions that are not accessible by epicardial mapping, noncontact endocardial mapping performed through a balloon catheter may provide a more comprehensive description of atrial activity. We developed a computer model of the canine right atrium to compare epicardial and noncontact endocardial mapping. The model was derived from an experiment in which electroanatomical reconstruction, epicardial mapping (103 electrodes), noncontact endocardial mapping (2048 virtual electrodes computed from a 64-channel balloon catheter), and direct-contact endocardial catheter recordings were simultaneously performed in a dog. The recording system was simulated in the computer model. For simulations and experiments (after atrio-ventricular node suppression), activation maps were computed during sinus rhythm. Repolarization was assessed by measuring the area under the atrial T wave (ATa), a marker of repolarization gradients. Results showed an epicardial-endocardial correlation coefficients of 0.80 and 0.63 (two dog experiments) and 0.96 (simulation) between activation times, and a correlation coefficients of 0.57 and 0.46 (two dog experiments) and 0.92 (simulation) between ATa values. Despite distance (balloon-atrial wall) and dimension reduction (64 electrodes), some information about atrial repolarization remained present in noncontact signals.

Echocardiographic assessment of cardiac performance in response to high altitude and development of subclinical pulmonary edema in healthy climbers.

BACKGROUND: Data regarding the effect of high altitude on heart function are sparse and conflicting. We aimed to assess the right and left ventricular responses to altitude-induced hypoxia and the occurrence of subclinical pulmonary edema. METHODS: Echocardiography was performed according to protocol on 14 subjects participating in an expedition in Nepal, at 3 altitude levels: Montreal (30 m), Namche Bazaar (3450 m), and Chukkung (4730 m). Systematic lung ultrasound was performed to detect ultrasound lung comets. RESULTS: Pulmonary artery systolic pressure increased in all subjects between Montreal and Chukkung (mean 27.4 ± 5.4 mm Hg vs. 39.3 ± 7.7 mm Hg; P < 0.001). Right ventricular (RV) myocardial performance index (MPI) increased significantly (0.32 ± 0.08 at 30 m vs. 0.41 ± 0.10 at 4730 m; P = 0.046). A trend toward deteriorated RV free wall longitudinal strain was observed between Montreal and Chukkung (-25.9 [5.3%] vs. -21.9 [6.4%]; P = 0.092). The left ventricular early diastolic inflow velocity/atrial mitral inflow velocity and early diastolic inflow velocity/mean of the maximal early diastolic mitral annulus tissue doppler velocities ratios remained unchanged. At 4730 m, ultrasound lung comets were seen in all subjects except 1. None had clinical criteria for high-altitude pulmonary edema (HAPE). All altered parameters normalized after return to sea level. CONCLUSION: Subclinical HAPE is frequent in healthy lowlander climbers. This is the first study to document a trend towards decreased RV free wall strain and MPI increment at high altitude. Whether rising RV MPI is a physiologic adaptive mechanism to hypoxia or a pathologic response identifying HAPE-susceptible subjects needs further study.