Mechanisms of inappropriate defibrillator therapy in a modern cohort of remotely monitored patients.

INTRODUCTION: Defibrillator (ICD) technology and monitoring are evolving rapidly. We investigated the mechanisms of inappropriate ICD therapies in a modern cohort of patients followed at our institution via remote monitoring. METHODS: From September 2009 to March 2011, a total of 2,050 ICD patients (19,600 patient-months) were remotely followed. All events (shocks and antitachycardia pacing) were adjudicated by arrhythmia specialists. RESULTS: A total of 249 patients received ICD therapy (34% inappropriate therapy). Inappropriate ICD shocks affected 33 (1.6%) patients. There were a total of 249 inappropriate episodes in 85 patients. Supraventricular tachycardia (SVT) with 1:1 atrioventricular association was the predominant mechanism accounting for 133 episodes in 50 patients, followed by atrial fibrillation (97 episodes in 27 patients). T-wave oversensing (16 episodes in five patients), electromagnetic interference (two episodes in two patients), and ectopic beats (one episode in one patient) accounted for a small proportion of events. There were 35 arrhythmic episodes in five patients that could not be classified, all in patients with single-chamber devices. There were no differences in these results by device manufacturer. CONCLUSIONS: Despite many technological advances, inappropriate ICD shocks still occur but at very low rates and SVT with 1:1 atrioventricular association represents their most common mechanism.

Clinical predictors of late death in survivors of acute myocardial infarction.

Survivors of acute myocardial infarction have higher mortality rates than do the general population. This study examined the value of multiple clinical characteristics in predicting late death among patients who present with acute myocardial infarction.We reviewed the electronic medical records of patients who had been treated for acute myocardial infarction at our institution from 1992 through 2000. We abstracted the clinical, laboratory, electrocardiographic, echocardiographic, and treatment characteristics.Of 144 patients (79.2% men; 97.2% white; mean age, 63 +/- 14.2 yr) included in this analysis, 63 (43.8%) patients died during a follow-up period of 5.6 +/- 2.8 years (5 d-12.7 yr). Higher age (hazard ratio, 1.83 +/- 0.31 for every 10-year increase), elevated serum creatinine (hazard ratio, 2.87 +/- 0.76), and lower baseline left ventricular ejection fraction (hazard ratio, 0.74 +/- 0.21 for every 5% increase) were found to be predictors of late death after adjusting for the white blood cell count, the QRS duration, the presence of coronary revascularization or defibrillator implantation, and the history of coronary artery disease. Elevated white blood cell count predicted early but not late death. Patients with none of the above risk factors had 100% survival at 5 years, in comparison with 22.7% survival for those with 3 or more of the 4 risk factors identified above.In this study, we have identified clinical predictors of long-term survival after acute myocardial infarction that might help in prognostication, patient education, and risk modification.

Location of acute myocardial infarction and associated arrhythmias and outcome.

BACKGROUND: Cardiac arrhythmias and conduction abnormalities complicating acute myocardial infarction (AMI) have been associated with adverse prognosis in numerous reports. Small studies have frequently associated different arrhythmias with various distributions of myocardial infarctions. We analyzed a nationally representative hospital discharge database to evaluate the relationship between the location of AMI and the associated arrhythmias and conduction abnormalities and their impact on in-hospital mortality. METHODS: We searched the National Hospital Discharge Survey database for patients with a diagnosis of AMI and collected data on the associated arrhythmias and conduction abnormalities. In-hospital death was used as end point for analysis. RESULTS: A total of 21,807 patients, representing 2,632,217 hospital discharges in the United States, with a primary diagnosis of AMI from 1996 to 2003 were included in this analysis. Patients with inferior or posterior AMI were more likely to develop complete heart block compared to those with anterior or lateral AMI (3.7% vs 1.0%, hazard ratio [HR] = 3.9, p

Derivation and validation of a diagnostic model for the evaluation of left ventricular filling pressures and diastolic function using mitral annulus tissue Doppler imaging.

BACKGROUND: Several modalities to diagnose diastolic dysfunction by transthoracic echocardiography (TTE) exist. We compared the ratio of early mitral filling velocity (E) to early diastolic velocity by tissue Doppler imaging at the medial (E/E'm) and the lateral (E/E'l) mitral annulus and developed a model to diagnose elevated left ventricular end-diastolic pressure (LVEDP). METHODS: Sixty patients underwent same-day cardiac catheterization and TTE. Left ventricular end-diastolic pressure was recorded in addition to TTE data, including left atrial area (LAA), E/E'm, and E/E'l. An LVEDP >15 mm Hg was considered to be elevated and diagnostic of diastolic dysfunction. RESULTS: E/E'm had a significantly higher correlation (r = 0.68, P < .001) than did E/E'l (r = 0.46, P < .001). By univariate analysis, LAA >18.75 cm(2), E/E'l >11.2, and E/E'm >15.75 were found to be significant predictors of high LV filling pressure. By multivariate binary logistic regression model analysis, only E/E'm and LAA were independent predictors of LVEDP >15 mm Hg. The presence of 1 variable had a sensitivity of 95% and a specificity of 43.4%, whereas the presence of 2 variables had a sensitivity of 76.2% and a specificity of 100%. CONCLUSIONS: Use of a diagnostic model based on easily derived measurements such as E/E'm and LAA was a powerful noninvasive diagnostic modality for elevated LVEDP. Measurement of the mitral annulus velocity by tissue Doppler imaging at the medial aspect of the mitral valve appeared to be superior to that at the lateral aspect.

Risk of death and recurrent ventricular arrhythmias in survivors of cardiac arrest concurrent with acute myocardial infarction.

AIMS: Cardiac arrest (CA) is an indication for defibrillator (ICD) implantation unless it occurs in the context of an acute myocardial infarction (AMI). We investigated the ventricular arrhythmia (VA)-free survival of patients resuscitated from CA in the setting of AMI. METHODS: We reviewed a database of 1600 AMI and CA survivors from which 48 patients were identified as having concurrent CA and AMI (CA+AMI group). Those patients were matched by age, gender, race, and left ventricular ejection fraction (LVEF) to 96 patients with AMI but no CA (AMI group) and 48 patients with CA but no AMI (CA group). RESULTS: Patients and controls were followed for 3.9+/-3.2 years. Patients in the 3 groups had similar baseline characteristics (age 63+/-14 yrs, 78% men, 98% white, 53% with CAD, LVEF 33+/-14%). The 5-year VA-free survival was 67%, 92%, and 80% for the CA+AMI, AMI, and CA groups, respectively, p<0.001. CONCLUSIONS: Patients with concurrent CA and AMI are at high risk of recurrent VA, with VA-free survival rates significantly worse than those of patients with AMI but no CA, and comparable to those of patients with CA outside the context of an AMI. Accordingly, these patients should be considered for ICD implantation.Condensed abstract Patients with concurrent CA and AMI were found to be at high risk of recurrent VA, with VA-free survival rates significantly worse than those of patients with AMI but no CA, and comparable to those with CA only. Accordingly, these patients should be considered for ICD implantation. .

Predictors of mortality amongst recipients of implantable cardioverter defibrillators for secondary prevention of cardiac arrest.

BACKGROUND: Implantable Cardioverter-defibrillators (ICD) reduce mortality in survivors of cardiac arrest (CA). We investigated the predictors of mortality after ICD implantation in survivors of CA. METHODS: Retrospective review of clinical records and social security death index of all patients who received an ICD in a preexisting database of survivors of CA at the University of Pittsburgh Medical Center was performed. Multivariate analyses using the Cox proportional hazard model were performed with backward elimination to identify independent predictors of the time to death, and Kaplan-Meier curves were plotted. RESULTS: Eighty patients (64 men) with a mean age of 64.4+/-12.5 years were followed for 4.7+/-2.3 years after ICD implantation. Survival rates were 93.8%, 65% and 50% at 1, 5, and 10 years, respectively. Independent predictors of time to death were determined to include age (hazard ratio (HR) = 1.91 per 10-year increase, p = 0.003), serum creatinine > or = 1.3 mg/dL (HR = 2.56, p = 0.004), and QRS width >120 ms (HR = 5.14, p = 0.012). CONCLUSIONS: In this sample of ICD recipients secondary to CA, older age, elevated serum creatinine, and wider QRS duration were independent predictors of mortality. The presence of more than one risk factor in the same patient was associated with higher mortality rates. Whether interventions such as biventricular pacing can offset this increase risk of death warrants further investigation.

Predictors of cardiac arrest occurring in the context of acute myocardial infarction.

BACKGROUND: Cardiac arrest (CA) concurrent with acute myocardial infarction (AMI) claims the life of many patients with coronary artery disease (CAD). In this study, we investigated the predictors of CA during AMI. METHOD: Patients admitted with CA concurrent with AMI (n = 31) were matched by age, gender, race, and left ventricular ejection fraction (LVEF) to patients with AMI but no CA (n = 70). All patients underwent coronary angiography. Binary logistic regression was used to identify independent predictors of CA during AMI. RESULTS: A total of 101 patients (age = 61 +/- 13 years, men 76%, Caucasians 98%, LVEF 33 +/- 12%) admitted to the University of Pittsburgh Medical Center with AMI were included in this analysis. Patients with CA concurrent with the AMI were more likely to have proximal rather than distal coronary artery culprit lesions (odds ratio (OR) = 7.2, P = 0.019). Other predictors of CA in the context of AMI included negative family history of CAD (OR = 8.0, P = 0.026) and absence of sinus rhythm upon hospital admission (OR = 5.1, P = 0.030). CONCLUSION: Proximity of culprit coronary lesion and presence of rhythm other than sinus rhythm at hospital admission are two strong predictors of CA in the context of AMI. The implication is that the mechanism of CA is primarily that of a large area of myocardial ischemia leading to lethal ventricular arrhythmia. Other predispositions such as genetic make-up cannot be ruled out.

Effect of end-stage renal failure and hemodialysis on mortality rates in implantable cardioverter-defibrillator recipients.

BACKGROUND: Most defibrillator (ICD) trials have excluded patients on hemodialysis (HD). It is therefore not known whether the ICD, when indicated, confers the same mortality benefit to HD and non-HD patients. METHOD: HD patients implanted with an ICD from July 2001 to June 2004 were matched by age, gender, left ventricular ejection fraction (LVEF), and class of heart failure to non-HD ICD recipients. RESULTS: Forty-six (16 on HD) patients (age = 65 +/- 15 yrs, LVEF = 30 +/- 14%, 44% in class III-IV HF) were followed for a mean of 30 +/- 16 months (range, 4-61 months) after ICD implantation. During this period, 12/16 HD versus 9/30 non-HD patients died (P = 0.006). The two-year mortality rates were 54% and 29% in the HD and non-HD groups, respectively (P = 0.01). After correcting for age, gender, race, LVEF, class of HF, and ICD indication (primary vs. secondary prevention) in a Cox regression model, HD remained a significant predictor of the time to death (HR = 2.9, adjusted P = 0.023). CONCLUSION: Despite having an ICD, HD patients have approximately a three-fold increase in total mortality and may therefore not extract the same survival benefits from the ICD as their non-HD counterparts. If duplicated in larger randomized trials, these results may demonstrate the futility of implanting defibrillators in HD patients.

A clinical risk score to predict the time to first appropriate device therapy in recipients of implantable cardioverter defibrillators.

BACKGROUND: To develop a risk score to predict the occurrence of appropriate defibrillator [implantable cardioverter-defibrillator (ICD)] therapies. A simple clinical score predicting the risk of appropriate ICD therapy is lacking. METHODS: A Cox regression model was developed from a database of ICD patients at a single tertiary center to predict the time to appropriate ICD therapy defined as shock or antitachycardia pacing. A risk score was derived from this model using half of the database and was validated using the other half. RESULTS: A total of 399 patients were entered into the database between July 2001 and February 2004. There were no statistically significant differences between the derivation (n = 200) and validation (n = 199) groups in any of the demographic or clinical variables recorded. The risk score included three independent variables: indication for ICD implantation (P = 0.03), serum creatinine level (P = 0.015), and QRS width (P = 0.028). The observed risk scores were highly predictive of time to ICD therapy in the validation group (P = 0.02). CONCLUSION: We describe a new clinical risk score that predicts the time to appropriate device therapy in ICD recipients of a single tertiary center hospital. The performance of this risk score needs to be investigated prospectively in a larger patient population.

Renal insufficiency predicts the time to first appropriate defibrillator shock.

BACKGROUND: Indications for implantable cardioverter defibrillator (ICD) implantation are expanding, but many primary and secondary ICD trials have excluded patients with advanced renal insufficiency. We investigated the effect of renal function on the incidence and time to first appropriate ICD shock. METHOD: We analyzed data from all new ICD implantations at a tertiary care center from July 2001 to December 2002. RESULTS: During a mean follow-up time of 445 +/- 285 days, 29 (13%) of 230 patients (age 63 +/- 14 years, 79% men, 77% white, 75% coronary artery disease, left ventricular ejection fraction 0.28 +/- 0.14) received 41 appropriate shocks. Patients were divided into tertiles according to their serum creatinine level. The 1-year incidence of appropriate ICD shock was 3.8%, 10.8%, and 22.7% in the first, second, and third tertiles, respectively (P = .003). Using the same cut off values of serum creatinine, the 1-year incidence of appropriate ICD therapy (shock and antitachycardia pacing) was 8.8%, 20.8%, and 26.3% (P = .02). After correcting for age, sex, race, left ventricular ejection fraction, indication for ICD implantation, and use of beta-blockers in a Cox regression model, serum creatinine was still an independent predictor of the time to first appropriate ICD shock (hazard ratio 6.0 for the third compared with the first tertile, P = .001). CONCLUSION: Renal insufficiency is a strong predictor of appropriate ICD shocks. Defibrillator therapy should therefore not be withheld based on the presence of this comorbidity. The mechanisms underlying the relationship between renal function and ventricular arrhythmias deserve further investigation.

Noncardiac surgery and the risk of death and other cardiovascular events in patients with hypertrophic cardiomyopathy.

BACKGROUND: There is a paucity of reports evaluating the perioperative risk of noncardiac surgery in patients with hypertrophic cardiomyopathy (HCM). HYPOTHESIS: The study was undertaken to evaluate the incidence of acute myocardial infarction (MI) and all-cause inhospital mortality following noncardiac surgery in patients with HCM. METHODS: We searched the National Hospital Discharge Survey database for patients with a diagnosis of HCM who had undergone noncardiac surgery. Cases were matched by age, gender, and year of surgery. Death or acute MI were used as endpoints for analysis. RESULTS: From 1996 to 2002, 227 patients with HCM were matched with 554 controls (representing national estimates of 25,874 HCM and 50,326 controls patients). Patients with HCM were more likely than controls to have a history of atrial fibrillation (22.7 vs. 10.6%, p < 0.001) and of congestive heart failure (CHF) (24.2 vs. 14.1%, p < 0.001). The in-hospital incidence of death or MI was higher in patients with HCM than in controls (6.7 vs. 2.5%, p < 0.001 for death and 2.2 vs. 0.3%, p < 0.001 for MI). After correcting for age, gender, race, presence of hypertension, diabetes mellitus, history of coronary artery-disease, history of CHF, atrial fibrillation, and ventricular arrhythmias in a multivariate binary logistic regression model, the presence of HCM increased the odds of death by 61% (odds ratio [OR] = 1.61, 95% confidence interval [CI] 1.46-1.77, p < 0.001), and almost tripled the odds of the combined endpoint of death or MI (OR = 2.82, 95% CI 2.59-3.07, p < 0.001). CONCLUSION: The presence of HCM significantly increases the risk of death and MI associated with noncardiac surgery. Patients with HCM undergoing elective procedures may require more careful preoperative assessment and perioperative monitoring. The impact of the severity of HCM on outcomes of noncardiac surgery needs further study.

Relation of advanced heart failure symptoms to risk of inappropriate defibrillator shocks.

Inappropriate implantable cardioverter-defibrillator (ICD) shocks continue to be a major source of distress to patients and a drain on the health care system. Expanding indications for ICD implantation include a large portion of patients with heart failure. This study investigated the relation between inappropriate ICD shocks and the severity of heart failure symptoms. Predictors of the time to first inappropriate ICD therapy were investigated in 230 consecutive patients implanted in 2001 and 2002. Thirty-two patients received 42 inappropriate shocks during a median follow-up of 501 days. Inappropriate shocks were due to atrial fibrillation (AF) or tachycardia (n = 31), other supraventricular tachycardias (n= 6), sinus tachycardia (n = 3), and noise or double counting (n = 2). The time to first inappropriate ICD shock was earliest in patients with advanced classes of heart failure (1- and 2-year shock-free survival of 79% and 70% for patients in New York Heart Association [NYHA] class III or IV vs 92% and 88% for patients in NYHA class I or II, respectively, p = 0.02). After correcting for age, gender, the presence of coronary artery disease, the presence of AF, the use of beta blockers, and indication for ICD implantation in a Cox regression model, advanced heart failure (NYHA class III or IV) remained an independent predictor of first inappropriate ICD shocks (hazard ratio 2.7, p = 0.01). Other predictors of the time to first inappropriate ICD shock included the presence of AF as the baseline rhythm at the time of the ICD implantation and the absence of coronary disease. In conclusion, inappropriate ICD shocks are predominantly due to AF. Advanced heart failure is an independent predictor of the time to first inappropriate ICD shocks. The effect of ICD programming and antiarrhythmic drug therapy on the incidence of inappropriate shocks deserves further investigation.

Indications for internal cardioverter defibrillator implantation predict time to first shock and the modulating effect of beta-blockers.

BACKGROUND: Patients receive implantable cardioverter defibrillator (ICD) for varying indications. Whether these indications influence the time to first ICD shock is suspected but not confirmed. The modulating effect of beta-blockers on shock-free survival is not fully elucidated. METHOD: A retrospective analysis of 230 consecutive patients (age 63 +/- 14 years, 79% men, 75% ischemic, 70% beta-blockers) implanted with an ICD was performed. Patients were divided into 4 groups depending on the ICD indication: groups A (secondary prevention of sudden death), B (left ventricular ejection fraction < or = 35% and positive electrophysiology study [EPS]), C (left ventricular ejection fraction < or = 35% and negative EPS or no EPS performed), and D (patients who did not meet inclusion criteria for groups A, B, or C). Time to shock was analyzed by the Kaplan-Meier method. RESULTS: During a mean follow-up of 489 +/- 280 days, 57 (24.7%) patients received 82 shocks (49% appropriate). The 1-year shock-free survival for patients in groups A, B, C, and D were 57%, 77%, 79%, and 91%, respectively (P = .03), for total shocks and 75%, 92%, 92%, and 100%, respectively (P = .007), for appropriate shocks. For patients in group A, the use of beta-blockers increased the 1-year shock-free survival from 48% to 61% for total shocks and from 65% to 79% for appropriate shocks. CONCLUSION: Time to first shock is determined by the indication for ICD implantation and is not predicted by the results of EPS. Patients with secondary indications for ICD implantation are at highest risk of shocks and may deserve consideration for prophylactic antiarrhythmic drugs. beta-Blockers increase the time to first ICD shock in patients implanted for secondary prevention of sudden death.

Hip fractures in lebanese patients: determinants and prognosis.

Hip fractures are the most costly of osteoporotic fractures, but little is known about their epidemiology in the Middle East. Hip fracture patients and controls with osteoarthritis admitted to our institution from 1992 to 2002 were studied. Information on gender, age, type of fracture, comorbid conditions, and medications use was obtained. The mean age for hip fracture patients (n = 274) was 72.1(8.5) yr, and for controls (n = 112), it was 71.1(4.4) yr, two-thirds of fractures occurred in women. Fractures were 59% intertrochanteric, 34% femoral neck, and 7% subtrochanteric, with no gender differences. Hip fracture patients were more likely to have had a prior fracture and to suffer from neurological, gastrointestinal, or renal comorbidities, as compared to controls. Less than 10% of hip fracture patients received any therapy for osteoporosis, either on admission or discharge. In a subset of patients with follow-up, the mortality rate was 47% in subjects with hip fracture, and most deaths occurred within the first year postoperatively. Gender but not fracture type affected mortality. Lebanese patients with hip fractures are younger, more likely to sustain intertrochanteric fractures, and experience higher mortality than Western counterparts. Few subjects received osteoporosis therapy. This study carries important public health implications on the management of hip fracture in subjects from Lebanon and, possibly, the Middle East.

Effects of race and health insurance on the rates of pacemaker implantation for complete heart block in the United States.

Although indicated for adults with complete heart block, pacemaker implantation is not always practiced. There are gross discrepancies by race, type of health insurance coverage, and size of hospital of admission in the utilization of pacemakers.