Left Atrial Cardiomyopathy - A Challenging Diagnosis

Abstract

Left atrial cardiomyopathy (LACM) has been an ongoing focus of research for several years. There is evidence that LACM is responsible for atrial fibrillation and embolic strokes of undetermined sources. Therefore, the correct diagnosis of LACM is of clinical importance. Various techniques, including electrocardiography, echocardiography, cardiac magnetic resonance imaging, computed tomography, electroanatomic mapping, genetic testing, and biomarkers, can both identify and quantify structural, mechanical as well as electrical dysfunction in the atria. However, the question arises whether these techniques can reliably diagnose LACM. Because of its heterogeneity, clinical diagnosis is challenging. To date, there are no recommendations for standardized diagnosis of suspected LACM. However, standardization could help to classify LACM more precisely and derive therapeutic directions to improve individual patient management. In addition, uniform diagnostic criteria for LACM could be important for future studies. Combining several parameters and relating them seems beneficial to approach the diagnosis of LACM. This review provides an overview of the current evidence regarding the diagnosis of LACM, in which several potential parameters are discussed and, consequently, a proposal for a diagnostic algorithm is presented.

Keywords: atrial cardiomyopathy; atrial fibrillation; diagnosis; diagnostic algorithm; embolic stroke of undetermined source.

FIGURE 1

Illustration of LACM as a composite entity of atrial fibrosis, mechanical dysfunction, and electrical dysfunction. Assessment of entities is achieved through different methods. CT, computed tomography; ECG, electrocardiology; f-wave, fibrillatory wave; LA, left atrial/let atrium; LAA, left atrial appendage; LACM, left atrial cardiomyopathy; MRI, magnetic resonance imaging; PET-CT, cardiac positron emission tomography – computed tomography.

FIGURE 2

Examples of ECG changes that are indicative of left atrial cardiomyopathy. (A) pronounced P-wave terminal force in lead V1 ≤ –4,000 μV × ms (multiplying the amplitude of the second term of the P-wave by the width of this term). (B) Prolonged P-wave duration (≥120 ms) and double peaked morphology. (C) “Coarse” atrial fibrillation with an amplitude of > 0.1 mV. (D) Example of an advanced interatrial block, defined as P-wave duration ≥ 120 ms with simultaneous biphasic morphology in the inferior leads.

FIGURE 3

Examples of echocardiographic measurements for the detection of left atrial cardiomyopathy. (A) Measurement of diameter in left atrial diastole. (B) Measurement of left atrial volume in left atrial diastole. (C) Transmitral inflow profile in left ventricular diastole: the first wave represents the E wave (passive inflow of blood into the left ventricle), the second wave represents the A wave (active contraction of the left atrium). (D) Tissue Doppler imaging of the movements of the left ventricular myocardium, in combination with the measurements from (C) the function of the atrium and the left ventricular end-diastolic pressure can be estimated. (E) Strain analysis of the left atrium. (F) Measurement of the PA-TDI interval from the beginning of the P-wave (as the onset of electrical activity of the atrium) to the peak of the a′-wave (mechanical response of atrial contraction).

FIGURE 4

Findings on transesophageal examination suggestive of left atrial cardiomyopathy. (A) Reduced blood flow in the ostium of the left atrial appendage. (B) Evidence of spontaneous echo contrast in the left atrial appendage. (C) Evidence of thrombus in the left atrial appendage.

FIGURE 5

Examples of MRI examinations of the left atrium: left atrial tissue fibrosis based on 3D delayed enhancement magnetic resonance imaging scans. Normal left atrial wall is displayed in blue, fibrotic changes are in red and white. Amounts of fibrosis as a percentage of the total left atrial wall volume. (A) Utah stage 1 (1%). (B) Utah stage 3 (27%). (C) Utah stage 4 (36%). With the friendly support of Dr. Misagh Piran (Herz- und Diabeteszentrum Nordrhein-Westfalen, Ruhr-Universität Bochum).

FIGURE 6

Examples of low-voltage areas in endocardial mapping of left atrium in patients with sinus rhythm who underwent pulmonary vein isolation: normally conducting atrial myocardium is colored purple, low voltage areas (defined as zones with an amplitude of electrical perception of ≤ 0.5 mV) are colored differently. (A) Example of a left atrium almost without low voltage areas. (B) Example of a severely diseased left atrium with low voltage areas > 10%.

FIGURE 7

Illustration of the underlying risk factors for left atrial cardiomyopathy. AF, atrial fibrillation; LACM, left atrial cardiomyopathy.

FIGURE 8

Proposal for a diagnostic algorithm for atrial cardiomyopathy based on the results of previous studies. APW, amplified P-wave; ESUS, embolic stroke of undetermined source; LA, left atrium/left atrial; PA-TDI, total atrial conduction time assessed by tissue doppler imaging; PTFV1; P-wave terminal force in lead V1.