Association of myocardial ischemia and coronary angiographic lesions with increased left atrial dimension during exercise tolerance tests among patients without known coronary heart disease

Relationship of left atrial expansion index to exercise tolerance, pretest probability of restenosis, and positive predictive value of treadmill test in coronary artery disease

BACKGROUND

Whether left atrial (LA) expansion index is associated with coronary restenosis, and exercise capacity (EC) reduction in coronary artery disease has not been established.

METHODS

This study analyzed 342 consecutive patients who had received a coronary stent implant. A treadmill exercise test (TET) was administered in all participants. The LA expansion indices were measured immediately before and after TET. Maximal EC measured on a breath-by-breath basis by a metabolic cart with gas analyzers and recorded as metabolic equivalent task. All patients with positive TET results received angiography, and those with restenosis received complete revascularization by either percutaneous coronary intervention (PCI) or bypass surgery. The LA expansion index and EC before and 1 month after PCI were then compared.

RESULTS

Out of 342 patients, 74 had positive TET results, and 54 had restenosis in angiography. Low LA expansion index was associated with poor EC. In patients with LA expansion index > 200%, only 5% had restenosis with 38.5% positive predictive value (PPV) of TET. In patients with LA expansion index < 100%, however, 64.3% had restenosis with 94.7% PPV of TET. Restenosis induced low pre-TET LA expansion index and further decline during TET. The LA expansion index significantly (P .001) improved from 133 ± 64% before PCI to184 ± 86% after PCI, and the improvement corresponded with EC recovery. A 10% reduction in LA expansion index was associated with a 15% increase in pretest probability of restenosis.

CONCLUSION

The LA expansion index is associated with EC, pretest probability of restenosis, and PPV of TET. Revascularization improves both EC and LA expansion index.

Left atrial volume and index by multi-detector computed tomography: comprehensive analysis from predictors of enlargement to predictive value for acute coronary syndrome (ROMICAT study)

OBJECTIVES

We aimed to identify the predictors of left atrial (LA) enlargement by multi-detector computed tomography (CT) and determine its association and predictive value for acute coronary syndrome (ACS).

BACKGROUND

LA enlargement is associated with myocardial ischemia and coronary artery disease (CAD) and is a strong predictor for cardiovascular events. These studies were performed primarily with echocardiography. With the rise of cardiac CT, LA volume can be readily measured.

METHODS

In 377 emergency department patients with chest pain, we performed 64-slice CT for coronary artery assessment. We derived LA volumes (LAV(max), LAV(min)) and indices (LAVI(max), LAVI(min)) using a threshold-based volumetric method.

RESULTS

Subjects, with cardiac risk factors or CAD by CT, had larger LA (ΔLAV(max) 9.1 ml, p=0.004; ΔLAV(min) 8.1 ml, p=0.001; ΔLAVI(max) 3.3 ml/m(2), p=0.03; ΔLAVI(min) 3.4 ml/m(2), p=0.006) than controls. Predictors of LA enlargement were related to risk factors for diastolic dysfunction. ACS risk was greater in patients with top quartile LAV(max) (odds ratio [OR] 3.4, p=0.02) and LAV(min) (OR 4.7, p=0.01) than lowest quartile, but not when indexed. Similarly, the predictive values of LA volumes were incrementally better when added to CT finding of indeterminate stenosis (LAV(max): C statistic 0.62 to 0.70, p=0.046; LAV(min): C statistic 0.65 to 0.73, p=0.008), but not when indexed.

CONCLUSIONS

Risk factors related to diastolic dysfunction are independent predictors of LA enlargement. LA enlargement by volumes are associated with a 3-5 fold increase risk for ACS and have incremental value for predicting ACS when added to the CT finding of indeterminate stenosis.

Formulaic quantification of echocardiographic left atrial volume

INTRODUCTION

The association between increasing severity in abnormal atrial depolarization and left atrial (LA) volume derived by transthoracic echocardiogram (TTE) has been described through the following regression formula: LA end-systolic volume index (LAVI [milliliter]) = 8.0 + 0.2 (P-wave duration [millisecond]) (r = 0.47; P = .0002). However, prospective assessment of this formula has not been validated among inpatients outside the institution where it was first derived.

METHODS

We prospectively obtained 12-lead electrocardiograms (ECGs) and TTEs on consecutive inpatients who were scheduled for nonemergent echocardiographic assessment. P waves were assessed independently to the nearest 10 milliseconds for application of the formula with a Bland-Altman plot. P-wave durations were obtained specifically from lead II and also from the any lead that yielded the widest measurement.

RESULTS

After excluding those with poor ECG tracing and TTE images, 72 patients were studied. We found a strong formulaic correlation with LAVI by TTE when maximal P-wave measurements were obtained from any ECG lead (r = 0.67; P < .0001) and more so, when restricted only to lead II (r = 0.89; P < .0001). Correlation was strongest when there was no or minimal difference between P-wave measurements in lead II and all other leads (r = 0.84; P < .0001 for no difference vs r = 0.67; P < .0001 for 60-millisecond difference). The Bland-Altman plot showed good agreement of LAVI assessment using the formulaic estimation when compared to TTE measurements derived by Simpson's rule (coefficient of reproducibility for 2 SD equivalent to 8.8% for lead II and 11.4% for any lead).

CONCLUSION

There is good agreement and correlation between formulaic estimation and that of TTE for LAVI among inpatients. Such quantification of LA size not only serves as an indirect asset that could perhaps supplement TTE measurements in certain circumstances but also can facilitate risk stratification of patients.

Relation of recurrence of atrial fibrillation after non-ST-elevation acute myocardial infarction to left atrial abnormality

Atrial fibrillation (AF) is common during the course of acute myocardial infarction and is associated with left atrial (LA) dilatation. However, the role of LA depolarization abnormality on the electrocardiogram (ECG) in the setting of LA dilatation was not studied in this context. Patients admitted with non-ST-segment elevation myocardial infarction (NSTEMI) who developed new-onset AF (International Classification of Diseases, Ninth Revision code 427.31) were prospectively identified. Baseline ECGs and echocardiograms before the admission event were reviewed. Follow-up was directed toward pertinent cardiovascular events, atrial tachyarrhythmias, and death as end points. Of 101 patients with NSTEMI who had new-onset AF, 88 had current echocardiograms and 69 had LA dilatation (78%). Total follow-up was 24 months (mean 21.4). Prolonged P-wave duration (> or =110 ms) and decreased left ventricular fractional shortening were most significant in those with LA dilatation and were independently associated with AF. In those with LA dilatation, the prevalence of such abnormal atrial depolarization on ECGs was 56%. AF (43% vs 15%; p = 0.03) and heart failure (63% vs 35%; p = 0.03) occurred more often in this subset, but there was no difference in mortality. However, the overall prevalence of late cardiovascular complications in this subset was higher (71% vs 45%; p = 0.02) compared with that of immediate complications (20% vs 26%; p = 0.60). In conclusion, there is higher recurrence of AF in patients with NSTEMI who have a combination of electrocardiographic and echocardiographic LA abnormalities compared with those without.

Differences in echocardiographic indices between patients with partial and advanced interatrial conduction delay

Partial interatrial block (IAB) (P wave > or =110 ms) is a marker of left atrial abnormality. A similar association among patients with advanced IAB (biphasic P waves > or =110 ms in leads II, III, and aVF) is unknown. The authors screened 27 consecutive patients for advanced IAB with transthoracic echocardiograms (TTEs). Of those, 19 who had repeat TTEs after 2 years formed our study cohort. The authors used 44 consecutive controls with partial IAB who had been similarly screened and had follow-up TTEs 2 years apart. TTE parameters were comparable at baseline between groups but were expectedly different on follow-up. When change (delta value) in these indices was compared, however, only left atrial dimension remained significant (advanced 0.07+/-0.06 mm vs partial IAB 0.03+/-0.06 mm; P=.03). Further study over a longer duration is warranted to ascertain if advanced IAB patients would benefit from follow-up noninvasive cardiac imaging for appropriate risk stratification.