Left atrium remodeling after acute myocardial infarction (results of the GISSI-3 Echo Substudy)

Left Atrial Remodeling Following ST-Segment-Elevation Myocardial Infarction Correlates With Infarct Size and Age Older Than 70 Years

Background Following myocardial infarction, left ventricular remodeling (LVR) is associated with heart failure and cardiac death. At the same time, left atrial (LA) remodeling (LAR) is an essential part of the outcome of a wide spectrum of cardiac conditions. The authors sought to evaluate the correlates of LAR and its relationships with LVR after myocardial infarction. Methods and Results This is a retrospective analysis of 320 of 443 patients enrolled for study of LVR after ST-elevation myocardial infarction. Left ventricular (LV) volumes, infarct size and LA volume index were assessed by cardiac magnetic resonance imaging during index hospitalization (day 6 [interquartile range, 4-8]) and after a 3-month follow-up. LAR was studied using a linear mixed model for repeated measurements. Overall, there was a decrease in LA volume index between 6 days and 3 months (43.9±10.4 mL versus 42.8±11.1 mL, P=0.003). Patients with changes in LA volume index >8% over time were older, with greater body mass index, lower LV ejection fraction, and larger infarct size. Unadjusted predictors of LAR were age older than 70 years, infarct size, anterior infarction, time to reperfusion, history of hypertension, LV end-diastolic volume, and heart failure at day 6. Independent correlates were age older than 70 years (3.24±1.33, P=0.015) and infarct size (2.16±0.72 per 10% LV, P<0.001). LA remodeling was correlated with LV remodeling (r=0.372, P<0.001), but neither LA nor LV volumes at day 6 were related to LVR or LAR, respectively. Conclusions The authors found LA changes to occur in the months after myocardial infarction, with an overall decrease in LA volumes. While LAR coincided with LVR, the correlates for LAR were age older than 70 years and larger infarct size.

Association Between Electrocardiographic Left Atrial Enlargement and Echocardiographic Left Atrial Indices Among Hypertensive Subjects in a Tertiary Hospital in South South Nigeria

INTRODUCTION

Left atrial (LA) enlargement poses a clinically significant risk of adverse cardiovascular outcomes for patients. To maximize the utility of LA size in diagnosis, its accurate measurement using electrocardiogram (ECG) and echocardiogram (ECHO) to assess LA linear diameter and LA volumes is expedient. The LA volumes correlate better than LA linear diameter with diastolic function variables. It is therefore expedient to use LA volumes routinely in assessing LA size as they may detect early and subtle changes in LA size and function.

METHODS

A descriptive cross-sectional study was conducted on 200 adult hypertensive patients attending the outpatient cardiology clinic at Delta State University Teaching Hospital, Oghara, Nigeria, irrespective of blood pressure control and duration of hypertension whether on antihypertensive medications or not. The SPSS version 22 (IBM Corp., Armonk, NY, USA) was used for data management and analysis.

RESULT

There was a significant association between electrocardiographic left atrial (ECG-LA) enlargement and echocardiographic left atrial (ECHO-LA) size (LA linear diameter and LA maximum volume) in the study. Logistic regression analysis showed a significant odds ratio for all associations. With LA linear diameter as standard for assessing LA enlargement, the ECG had a sensitivity of 19%, specificity of 92.4%, a positive predictive value of 51%, and a negative predictive value of 73% in detecting LA enlargement. Using ECHO-LA maximum volume as a standard for assessing LA enlargement, the ECG had a sensitivity of 57.3%, a specificity of 67.7%, a positive predictive value of 42.9%, and a negative predictive value of 79% in detecting LA enlargement. The LA maximum volume showed relatively higher sensitivity and negative predictive values while LA linear diameter showed relatively higher specificity and positive predictive values.

CONCLUSION

A good association exists between ECG-LA enlargement and ECHO-LA enlargement. However, in ruling out LA enlargement on ECG, it is better to use LA maximum volume as a standard rather than the LA linear diameter.

Left atrial disease and left atrial reverse remodelling across different stages of heart failure development and progression: a new target for prevention and treatment

The left atrium is a dynamic chamber with peculiar characteristics. Stressors and disease mechanisms may deeply modify its structure and function, leading to left atrial remodelling and disease. Left atrial disease is a predictor of poor outcomes. It may be a consequence of left ventricular systolic and diastolic dysfunction and neurohormonal and inflammatory activation and/or actively contribute to the progression and clinical course of heart failure through multiple mechanisms such as left ventricular filling and development of atrial fibrillation and subsequent embolic events. There is growing evidence that therapy may improve left atrial function and reverse left atrial remodelling. Whether this translates into changes in patient's prognosis is still unknown. In this review we report current data about changes in left atrial size and function across different stages of development and progression of heart failure. At each stage, drug therapies, lifestyle interventions and procedures have been associated with improvement in left atrial structure and function, namely a reduction in left atrial volume and/or an improvement in left atrial strain function, a process that can be defined as left atrial reverse remodelling and, in some cases, this has been associated with improvement in clinical outcomes. Further evidence is still needed mainly with respect of the possible role of left atrial reverse remodelling as an independent mechanism affecting the patient's clinical course and as regards better standardization of clinically meaningful changes in left atrial measurements. Summarizing current evidence, this review may be the basis for further studies.

Early left atrial dysfunction is associated with suboptimal cardiovascular health

AIMS

Two-dimensional speckle-tracking echocardiography can assess left atrial (LA) function by measuring atrial volumes and deformation parameters (strain, strain rate). This cross-sectional analysis explores the association between ideal CV health (CVH), LA function, and systemic biomarkers in healthy individuals from the Chilean MAUCO Cohort.

METHODS

We enrolled 95 MAUCO participants with different levels of CVH (mean age: 51 ± 8 years). We categorized participants into low or high CVH groups: A: 0-2, or B: 3-6 CVH risk factors. 2D echocardiography, glucose, insulin, total cholesterol, triglycerides, proBNP, hsCRP, insulin resistance index (HOMA), and right and left atrial strain (RASs and LASs, respectively) were determined.

RESULTS

LASs was lower in Group A, while systolic and diastolic blood pressure (BP), body mass index (BMI), insulin, HOMA, total cholesterol, triglycerides, and LV and RV end-diastolic volume were significantly higher in Group A than Group B (P < .01). Change in LASs was inversely correlated with insulin (P = .040), HOMA (P = .013), total cholesterol (P = .039), glycemia (P = .018), and BMI (P = .0.037).

CONCLUSION

LASs during the reservoir phase was diminished in subjects with a lower level of CVH. Higher insulin, HOMA, total cholesterol, glycemia, and BMI values were associated with decreased LA deformation during the reservoir phase. Morphofunctional alterations of the LA were also identified in the group with suboptimal CVH, as well as BP values in the range of hypertension. LA dysfunction in an asymptomatic population, along with metabolic syndrome, could be an early event in the continuum of CV damage.

Left atrial volume index: Can it provide additional prognostic information in ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention?

INTRODUCTION

We sought to assess the prognostic impact of left atrial (LA) size on long-term outcomes of ST-segment elevation myocardial infarction (STEMI).

METHODS

We studied 200 consecutive patients admitted to a single center between January 2010 and December 2014 with non-fatal STEMI treated with primary percutaneous coronary intervention (pPCI) who underwent a comprehensive echocardiographic examination at discharge. LA volume was estimated by the area-length method. The left atrium was classified as normal, mildly, moderately or severely enlarged by LA volume index (LAVI). The endpoints were defined as all-cause mortality, a cardiac composite endpoint (all-cause mortality, reinfarction, unplanned revascularization and hospitalization for heart failure) and a cardiovascular composite endpoint (cardiac endpoint plus atrial fibrillation and ischemic stroke) during follow-up.

RESULTS

In this STEMI population, 58% had normal LA size, 22.5% had mild LA enlargement, 10% had moderate LA enlargement and 9.5% had severe LA enlargement. During a median follow-up of 28 (IQR 21-38) months, 14 (7.0%) patients died, 53 (26.5%) had the cardiac and 58 (29%) the cardiovascular composite endpoints. There was a stepwise increase in the incidence of all-cause mortality (p=0.020) and both cardiac (p<0.001) and cardiovascular (p<0.001) endpoints with each increment of LAVI class. In multivariate analysis, severe LA enlargement by LAVI was an independent predictor of all-cause mortality (HR: 11.153; 95% CI: 1.924-64.642, p=0.007) and the cardiac (HR: 4.351; 95% CI: 1.919-9.862, p<0.001) and cardiovascular (HR: 4.351; 95% CI: 1.919-9.862, p<0.001) endpoints during follow-up.

CONCLUSIONS

This contemporary study confirms the prognostic effect of LA size at discharge, applying the most recent reference values in STEMI patients treated with pPCI.

Morphological features of the left atrial appendage in consecutive coronary computed tomography angiography patients with and without atrial fibrillation

The majority of intracardiac thrombi form in the left atrial appendage (LAA). Enlargement of this structure, together with certain morphological features, may indicate a predisposition to the formation of thrombi and subsequent cardioembolic stroke. Thus far, studies on LAA morphology have largely focused on those patients with atrial fibrillation (AF). Taking a different approach, we investigated the variation in LAA morphology in a consecutive patient population with and without AF. We evaluated 808 consecutive patients (529 females; mean age 52.5±9.9 years) who underwent coronary artery computed tomography angiography (CCTA), the majority of whom (749) had no history of AF. We assessed the length, lobe number, and morphological classification of their LAAs. Demographic data and medical histories were collated from medical records and then correlated with LAA morphology. The proportions of each of the four morphological classes of LAA for the overall vs. non-AF population were: WindSock, 62.3/61.5%; Cactus, 18.6/18.8%; ChickenWing, 10.0/10.0%; and CauliFlower, 9.2/9.6%. Age (p<0.001; r = 0.156) and female gender (p<0.001) were both found to be associated with an increased body surface area (BSA)-related LAA length. Male patients were more likely to manifest multi-lobed (p = 0.003) LAAs, and overweight patients with a greater number of multi-lobed LAA morphological classes (p = 0.010). No associations with morphological LAA features could be found for patients with diabetes, hypertension, or dyslipidemia. Nor did the size of the left atrium exhibit any correlation with BSA-related LAA length. In the overall and non-AF populations, aging and female gender were associated with longer BSA-indexed LAAs.

Methodological Gaps in Left Atrial Function Assessment by 2D Speckle Tracking Echocardiography

The assessment of left atrial (LA) function is used in various cardiovascular diseases. LA plays a complementary role in cardiac performance by modulating left ventricular (LV) function. Transthoracic two-dimensional (2D) phasic volumes and Doppler echocardiography can measure LA function non-invasively. However, evaluation of LA deformation derived from 2D speckle tracking echocardiography (STE) is a new feasible and promising approach for assessment of LA mechanics. These parameters are able to detect subclinical LA dysfunction in different pathological condition. Normal ranges for LA deformation and cut-off values to diagnose LA dysfunction with different diseases have been reported, but data are still conflicting, probably because of some methodological and technical issues. This review highlights the importance of an unique standardized technique to assess the LA phasic functions by STE, and discusses recent studies on the most important clinical applications of this technique.

Predictors and prognostic value of left atrial remodelling after acute myocardial infarction

PURPOSE

Left atrial (LA) volume is a strong prognostic predictor in patients following ST-segment elevation myocardial infarction (STEMI). However, the change in LA volume over time (LA remodelling) following STEMI has been scarcely studied. We sought to identify predictors for LA remodelling and to evaluate the prognostic importance of LA remodelling.

METHODS

This is a subgroup analysis from a randomised clinical trial that evaluated the cardioprotective effect of exenatide treatment. A total of 160 patients with STEMI underwent a cardiovascular MR (CMR) 2 days after primary angioplasty and a second scan 3 months later. LA remodelling was defined as changes in LA volume or function from baseline to 3 months follow-up. Major adverse cardiac events were registered after a median of 5.2 years.

RESULTS

Adverse LA minimum volume (LAmin) remodelling was correlated to the presence of hypertension, larger infarct size by CMR, higher peak troponin T, larger area at risk and adverse left ventricular (LV) remodelling. LA maximum volume (LAmax) remodelling was correlated to larger infarct size by CMR, higher peak troponin T, larger area at risk, larger LV mass, impaired LV function and adverse LV remodelling. Kaplan-Meier and Log Rank analyses showed that patients in the highest tertiles of LAmin or LAmax remodelling are at higher risk (0.030 and p=0.018).

CONCLUSIONS

After a myocardial infarction, LA remodelling reflects a parallel ventricular-atrial remodelling. Infarct size is a major determinant of LA remodelling following STEMI and adverse LA remodelling is associated with an unfavourable prognosis.

Evaluation of biatrial size and functions by different echocardiographic parameters in patients with acute coronary syndromes

After acute coronary syndromes (ACS), cardiac remodelling affecting not only ventricles but also both atria is an important problem associated with an increased risk for adverse cardiovascular outcomes. However, it is usually underestimated to evaluate atrial size and functions. The aim of the present study is to compare left and right atrial size and functions in ACS patients with healthy controls during transthoracic echocardiography by means of diameter, area and volume measurements, and pulsed-wave tissue Doppler imaging (TDI). 150 ACS patients (128 male, 22 female) and 25 healthy controls (19 male, 6 female) were enrolled into the study. Of the ACS patients, 75 had ST-segment elevation myocardial infarction (STEMI) and 75 had non-STEMI. Biatrial diameters, areas, and volumes were measured from different echocardiographic views. Atrial total emptying fraction and expansion index values were calculated from volume measurements. By the pulsed-wave TDI of the atrial walls; peak systolic (S'), peak early diastolic (E'), and peak late diastolic (A') velocities were measured. Almost all left atrial parameters for diameter, area, and volume measurements were higher in ACS patients. Similarly, they had higher values for the same right atrial parameters. Left and right atrial total emptying fraction and expansion index values were lower in ACS patients than controls. All left and right atrial walls had lower S' and E' velocities in ACS patients. ACS cause important alterations in the biatrial size and functions evaluated by echocardiographic diameter, area and volume measurements, and pulsed-wave TDI.

Left atrial expansion index predicts all-cause mortality and heart failure admissions in dyspnoea

AIMS

The power of left atrial (LA) parameters for predicting adverse events in relatively low-risk groups is not fully understood. This study investigated whether the LA expansion index predicts heart failure (HF) and all-cause mortality in subjects with dyspnoea.

METHODS AND RESULTS

Echocardiography was performed to identify causes of dypnoea in 1735 patients. The LA expansion index was calculated as (Volmax - Volmin) × 100%/Volmin, where Volmax was defined as the maximal LA volume and Volmin was defined as the minimal LA volume. The endpoints were 2-year frequencies of HF hospitalization and all-cause mortality. Over a median follow-up of 2.7 years, 91 participants reached endpoints. Rates of adverse events were exponentially proportional to the LA expansion index. For predicting adverse events, the LA expansion index was better than the maximal indexed LA volume and tissue Doppler parameters. Hospitalization for HF was independently associated with age, LVEF, pulmonary artery systolic pressure, LA expansion index, and history of prior HF. All-cause mortality was associated with age, pulmonary artery systolic pressure, and LA expansion index. Compared with the highest quartile of the LA expansion index, the lowest quartile had a 3.1-fold higher hazard of HF events and a 17.8-fold higher hazard of all-cause mortality.

CONCLUSIONS

The LA expansion index predicts adverse events in patients with dyspnoea. The prognostic power of the index exceeds that of other well-established echocardiographic parameters such as E/e' and maximal indexed LA volume. Trial registration NCT01171040.

Prognostic value of left atrium remodeling after primary percutaneous coronary intervention in patients with ST elevation acute myocardial infarction

The purpose of this study is to assess the relationship between left atrial (LA) size and outcome after acute myocardial infarction (AMI) in patients undergoing primary percutaneous coronary intervention (PCI) and to evaluate dynamic changes in LA size during long-term follow-up. Echocardiographic analyses were performed on 253 AMI patients (174 male and 79 female, 65.4 ± 13.7 yr) undergoing PCI. These subjects were studied at baseline and at 12 months. Clinical follow-up were done at 30.8 ± 7.5 months. We assessed LA volume index (LAVI) at AMI-onset and at 12-month. Change of LAVI was an independent predictor of new onset of atrial fibrillation or hospitalization for heart failure (P = 0.002). Subjects who survived the 12-month period displayed an increased LAVI mean of 1.86 ± 4.01 mL/m(2) (from 26.1 ± 8.6 to 28.0 ± 10.1 mL/m(2), P < 0.001). The subject group that displayed an increased LAVI correlated with a low left ventricular ejection fraction, large left ventricle systolic and diastolic dimensions and an enlarged LA size. In conclusion, change of LAVI is useful parameter to predict subsequent adverse cardiac event in AMI patients. Post-AMI echocardiographic evaluation of LAVI provides important prognostic information that is significantly greater than that obtained from clinical and laboratory parameters alone.

Incidence, determinants and consequences of left atrial remodelling after a first anterior myocardial infarction

BACKGROUND

Left atrial (LA) volume is an important predictor of mortality and morbidity after myocardial infarction (MI). However, the process of LA remodelling has not been extensively investigated.

AIMS

Our purpose was to analyse the incidence, determinants and consequences of LA remodelling in a cohort of patients with a first anterior MI enrolled in the modern era of MI management.

METHODS

We used data from 246 patients with a first anterior MI who were included in a prospective study on left ventricular (LV) remodelling (REVE-2). Serial echocardiographic studies were performed before discharge and at 3 months and 1 year after MI.

RESULTS

LA volume increased from 20.5±5.9 mL/m2 at baseline to 24.6±7.4 mL/m2 at 3 months (P<0.0001 versus baseline) and 25.4±7.6 mL/m2 at 1 year (P<0.0001 versus baseline). Patients with high LA volumes at baseline had higher LV volumes, decreased LV systolic function, increased E/Ea (early transmitral velocity/mitral annular early diastolic velocity ratio) and increased B-type natriuretic peptide concentration. By multivariable analysis, the sole independent predictor of change in LA volume from baseline to 1 year was peak creatine kinase concentration (P<0.0001). Patients with higher LA volumes at baseline were at higher risk of cardiovascular death or rehospitalization for heart failure during follow-up (P=0.015).

CONCLUSIONS

Despite modern therapeutic management, LA remodelling is common during the first 3 months after anterior MI. Patients with larger infarct size are at greater risk of LA remodelling after discharge.

Comparison of the accuracy of multidetector computed tomography versus two-dimensional echocardiography to measure left atrial volume

Left atrial (LA) volume is an important prognostic factor in cardiovascular disease. Multidetector computed tomography (MDCT) is an emerging cardiac imaging modality; however, its accuracy in measuring the LA volume has not been well studied. The aim of our study was to determine the accuracy of MDCT in quantifying the LA volume. A total of 48 patients underwent MDCT and 2-dimensional (2D) echocardiography (2DE) on the same day. The area-length and Simpson's methods were used to obtain the 2D echocardiographic LA volume. The LA volume assessment by MDCT was obtained using the modified Simpson's method. Four artificial phantoms were created, and their true volume was assessed by an independent observer using both imaging modalities. The correlation between the LA volume by MDCT and 2DE was significant (r = 0.68). The mean 2D echocardiographic LA volume was lower than the LA volume obtained with MDCT (2DE 79 +/- 37 vs MDCT 103 +/- 32, p <0.05). In the phantom experiment, the volume obtained using MDCT and 2DE correlated significantly with the true volume (r = 0.97, p <0.05 vs r = 0.96, p <0.05, respectively). However, the mean 2D echocardiographic phantom volume was 16% lower than the true volume (2DE, Simpson's method 53 +/- 24 vs the true volume 61 +/- 24, p <0.05). The mean volume calculated using MDCT did not differ from the true volume (MDCT 60 +/- 21 vs true volume 61 +/- 24, p = NS). 2DE appeared to systematically underestimate the LA volume compared to phantom and cardiac MDCT, suggesting that different normal cutoff values should be used for each modality. In conclusion, LA volume quantification using MDCT is an accurate and feasible method.

Effects of perindopril on cardiac remodelling and prognostic value of pre-discharge quantitative echocardiographic parameters in elderly patients after acute myocardial infarction: the PREAMI echo sub-study

AIMS

To determine (i) the effect of perindopril on several geometric and functional parameters of the left and right ventricles assessed by echocardiography in the unique Perindopril and Remodelling in Elderly with Acute Myocardial Infarction (PREAMI) population of post-acute myocardial infarction (AMI) elderly patients with preserved left ventricular (LV) function; and (ii) the prognostic predictors at pre-discharge derived from echo-Doppler measurements in the same population.

METHODS AND RESULTS

PREAMI included 1252 post-AMI patients (age 73 +/- 6 years, LV ejection fraction 59.1 +/- 7.7%) receiving optimal therapy after AMI, randomized to perindopril 8 mg/day (n = 631) or placebo (n = 621); n = 896 had complete echo-Doppler data. Outcome measures were clinical [death, heart failure (HF)] and standard echo-Doppler parameters. Pre-discharge LV end-diastolic volume (LVEDV) was similar: 81.1 +/- 23.1 (perindopril) and 79.6 +/- 22.7 mL (placebo). At 6 months and 1 year, LVEDV remained unchanged with perindopril (81.2 +/- 24.4 and 81.8 +/- 26.8 mL, respectively), but increased with placebo (83.0 +/- 25.3 and 83.6 +/- 25.7 mL, respectively, both P < 0.001 vs. baseline). Perindopril reduced cardiac sphericity vs. placebo (P = 0.015 at 6 months; P = 0.020 at 1 year). Classification regression tree analysis showed treatment as the most important predictor of remodelling. Multiple pre-discharge echocardiographic variables predicted the death/HF endpoint, independently of treatment (P < or = 0.05).

CONCLUSION

Remodelling occurs in post-AMI in elderly patients with normal LV function. Echo-Doppler variables at baseline have prognostic implications. Treatment with perindopril reduces progressive LV remodelling that can occur even in the case of small infarct size.

Left atrial volume provides independent and incremental information compared with exercise tolerance parameters in patients with heart failure and left ventricular systolic dysfunction

OBJECTIVE

Left atrial volume (LAV) is a powerful predictor of outcome in patients with chronic heart failure (CHF) independently of symptomatic status, age and left ventricular (LV) function. It is unknown whether LAV provides independent and incremental information compared with exercise tolerance parameters.

METHODS

273 patients with CHF (mean (SD) 62 (9) years; 13% female) prospectively underwent echocardiography and exercise testing with maximal oxygen consumption (Vo(2)). The primary end point was composite and included cardiac death, hospitalisation for worsening heart failure or cardiac transplantation.

RESULTS

At Cox proportional hazard analysis, LAV normalised for body surface area (LAV/BSA) was strongly associated with mortality (hazard ratio (HR) = 1.027 (95% CI 1.018 to 1.04), p<0.001). The predictive value of LAV/BSA was independent of Vo(2) and LV ejection fraction (EF) (HR = 1.014 (1.002 to 1.025), p = 0.02; HR = 0.95 (0.91 to 0.99), p = 0.02; HR = 0.89 (0.82 to 0.98), p = 0.02 for LAV/BSA, EF and Vo(2), respectively). Receiver operator characteristic (ROC) curve analysis identified the best cut-off values for prediction of the end point. LAV/BSA >63 ml, EF <30% and Vo(2) <16 ml/kg/min were considered to be risk factors. Patients with three risk factors had an HR of 38 (95% CI 11 to 129) compared with patients with no risk factors.

CONCLUSION

LAV provides powerful prognostic information incrementally and independently of Vo(2). LAV, EF and Vo(2 )can be used to build a risk prediction model, which can be used clinically.

Impact of myocardial perfusion on left atrial remodeling following primary angioplasty for acute myocardial infarction

OBJECTIVES

To investigate the impact of myocardial perfusion on left atrial remodeling and its determinants after primary percutaneous coronary intervention for acute myocardial infarction.

BACKGROUND

Left atrial volume is an important predictor of morbidity and mortality in acute myocardial infarction, while thrombolysis in myocardial infarction (TIMI) myocardial perfusion (TMP) grade is an angiographic index associated with infarct size and mortality. As yet, however, the relationship between TMP grade and left atrial remodeling has not been investigated.

METHODS

Conventional transthoracic echocardiography was performed in 105 patients (55+/-13 years old, 92 men) with acute myocardial infarction within 24 h and after 6 months (mean 9+/-4, range 6-29 months) following successful primary percutaneous coronary intervention. Absolute left atrial volume was calculated using an elliptical model. Myocardial perfusion was evaluated, using TMP grade, by visual assessment on the coronary angiogram. Patients were divided into three groups on the basis of myocardial perfusion status, as TMP 0/1 (n=36), TMP 2 (n=36) and TMP 3 (n=33).

RESULTS

No difference was observed between baseline and follow-up left atrial volumes in the overall study population (42.5+/-16.1 vs. 43.5+/-17.4 ml, P=0.519). As regards TMP grade, follow-up left atrial volume significantly increased in the TMP 0/1 group (43+/-17 vs. 54.6+/-1.1 ml, P<0.001) and significantly decreased in the TMP 3 group (42.9+/-15.7 vs. 35.5+/-12.2 ml, P=0.001) compared with initial values. No change was observed in left atrial volume in the TMP 2 group. Multivariate analysis showed that TMP grade (P<0.001) and anterior location of myocardial infarction (P<0.001) were independent determinants of left atrial remodeling.

CONCLUSIONS

These results suggest that poor myocardial perfusion and anterior location of myocardial infarction can affect left atrial remodeling in patients with acute myocardial infarction undergoing primary percutaneous coronary intervention. It appears that adequate myocardial perfusion is crucial to prevent left atrial remodeling, a poor prognostic factor in acute myocardial infarction.

Canine model of paroxysmal atrial fibrillation and paroxysmal atrial tachycardia

Both autonomic nerve activity and electrical remodeling are important in atrial arrhythmogenesis. Therefore, dogs with sympathetic hyperinnervation, myocardial infarction (MI), and complete atrioventricular block (CAVB) may have a high incidence of atrial arrhythmias. We studied eight dogs (experimental group) with MI, CAVB, and sympathetic hyperinnervation induced either by nerve growth factor infusion ( n = 4 dogs) or subthreshold electrical stimulation ( n = 4 dogs) of the left stellate ganglion. Cardiac rhythm was continuously monitored by a Data Sciences International transmitter for 48 (SD 27) days. Three normal control dogs were also monitored. Six additional normal dogs were used for histology control. Paroxysmal atrial fibrillation (PAF) and paroxysmal atrial tachycardia (PAT) were documented in all dogs in the experimental group, with an average of 3.8 (SD 3) episodes/day, including 1.3 (SD 1.6) episodes of PAF and 2.5 (SD 2.2) episodes of PAT. The duration averaged 298 (SD 745) s (range, 7–4,000 s). There was a circadian pattern of arrhythmia onset ( P < 0.01). Of 576 episodes of PAF and PAT, 236 (41%) episodes occurred during either sustained or nonsustained ventricular tachycardia (VT). Among these 236 episodes, 53% started before VT, whereas 47% started after the onset of VT. Normal dogs did not have either PAF or PAT. The hearts from the experimental group had a higher density of nerve structures immunopositive ( P < 0.01) for three different nerve specific markers in both right and left atria than those of the control dogs. We conclude that the induction of nerve sprouting and sympathetic hyperinnervation in dogs with CAVB and MI creates a high yield model of PAF and PAT.