How Often Does Apical Sparing of Longitudinal Strain Indicate the Presence of Cardiac Amyloidosis?

Arrhythmic Risk Stratification in Cardiac Amyloidosis: A Review of the Current Literature

Cardiac amyloidosis is the most frequent infiltrative disease caused by the deposition of misfolded proteins in the cardiac tissue, leading to heart failure, brady- and tachyarrhythmia and death. Conduction disorders, atrial fibrillation (AF) and ventricular arrhythmia (VA) significantly impact patient outcomes and demand recognition. However, several issues remain unresolved regarding early diagnosis and optimal management. Extreme bradycardia is the most common cause of arrhythmic death, while fast and sustained VAs can be found even in the early phases of the disease. Risk stratification and the prevention of sudden cardiac death are therefore to be considered in these patients, although the time for defibrillator implantation is still a subject of debate. Moreover, atrial impairment due to amyloid fibrils is associated with an increased risk of AF resistant to antiarrhythmic therapy, as well as recurrent thromboembolic events despite adequate anticoagulation. In the last few years, the aging of the population and progressive improvements in imaging methods have led to increases in the diagnosis of cardiac amyloidosis. Novel therapies have been developed to improve patients' functional status, quality of life and mortality, without data regarding their effect on arrhythmia prevention. In this review, we consider the latest evidence regarding the arrhythmic risk stratification of cardiac amyloidosis, as well as the available therapeutic strategies.

Limitations of apical sparing pattern in cardiac amyloidosis: a multicentre echocardiographic study

AIMS

Although impaired left ventricular (LV) global longitudinal strain (GLS) with apical sparing is a feature of cardiac amyloidosis (CA), its diagnostic accuracy has varied across studies. We aimed to determine the ability of apical sparing ratio (ASR) and most common echocardiographic parameters to differentiate patients with confirmed CA from those with clinical and/or echocardiographic suspicion of CA but with this diagnosis ruled out.

METHODS AND RESULTS

We identified 544 patients with confirmed CA and 200 controls (CTRLs) as defined above (CTRL patients). Measurements from transthoracic echocardiograms were performed using artificial intelligence software (Us2.AI, Singapore) and audited by an experienced echocardiographer. Receiver operating characteristic curve analysis was used to evaluate the diagnostic performance and optimal cut-offs for the differentiation of CA patients from CTRL patients. Additionally, a group of 174 healthy subjects (healthy CTRL) was included to provide insight on how patients and healthy CTRLs differed echocardiographically. LV GLS was more impaired (-13.9 ± 4.6% vs. -15.9 ± 2.7%, P < 0.0005), and ASR was higher (2.4 ± 1.2 vs. 1.7 ± 0.9, P < 0.0005) in the CA group vs. CTRL patients. Relative wall thickness and ASR were the most accurate parameters for differentiating CA from CTRL patients [area under the curve (AUC): 0.77 and 0.74, respectively]. However, even with the optimal cut-off of 1.67, ASR was only 72% sensitive and 66% specific for CA, indicating the presence of apical sparing in 32% of CTRL patients and even in 6% healthy subjects.

CONCLUSION

Apical sparing did not prove to be a CA-specific biomarker for accurate identification of CA, when compared with clinically similar CTRLs with no CA.

Current Therapies and Future Horizons in Cardiac Amyloidosis Treatment

PURPOSE OF REVIEW

Cardiac amyloidosis (CA) is a condition characterized by misfolding and extracellular deposition of proteins, leading to organ dysfunction. While numerous forms of CA exist, two subtypes dominate clinical prevalence: Transthyretin amyloid (ATTR) and immunoglobulin light chain amyloid.

RECENT FINDINGS

The current scientific landscape reflects the urgency to advance therapeutic interventions with over 100 ongoing clinical trials. Heart failure treatment is affected by CA phenotype with poor tolerance of otherwise frequently used medications. Treating comorbidities including atrial fibrillation and valvular disease remains a challenge in CA, driven by technical difficulties and uncertain outcomes. Tafamidis is the first ATTR-stabilizer approved with a rapidly growing rate of clinical use. In parallel, various new therapeutic classes are in late-stage clinical trials including silencers, antibodies and genetic therapy. Managing CA is a critical challenge for future heart failure care. This review delineates the current standard-of-care and scientific landscape of CA therapy.

Novel electrocardiographic criteria may render possible the more accurate recognition of cardiac amyloidosis

AIMS

The early diagnosis of cardiac amyloidosis (CA) is paramount, since there are effective therapies that improve patient survival. The diagnostic accuracy of classical electrocardiographic (ECG) signs, such as low voltage, pseudoinfarct pattern, and conduction disturbances in the diagnosis of CA, is inferior to that of the echocardiographic myocardial deformation criteria; therefore, our aim was to find more accurate novel ECG criteria for this purpose.

METHODS

We tested the diagnostic value of five novel ECG criteria, two of them devised by us, in 34 patients with confirmed CA (20 transthyretin amyloidosis and 14 AL amyloidosis) and 45 control patients with left ventricular hypertrophy on echocardiography due to hypertension, valvular aortic stenosis and hypertrophic cardiomyopathy. The following novel ECG criteria, that suggested CA, were tested: QRS amplitude in lead I < 0.55 mV (I < 0.55); QRS amplitude in lead aVR < 0.5 mV (aVR < 0.5); average QRS amplitude of leads I + aVR < 0.575 mV [(I + aVR) < 0.575]; average QRS amplitude of leads I + aVR/average QRS amplitude of leads V1-4 < 0.375 [(I + aVR)/(V1-4) < 0.375]; average QRS amplitude of leads I + aVR/longest intrinsicoid deflection in leads I,aVL,V1-6 < 0.0115 [(I + aVR)/I,aVL,V1-6ID < 0.0115].

RESULTS

The I < 0.55, aVR < 0.5, (I + aVR) < 0.575, (I + aVR)/(V1-4) < 0.375, (I + aVR)/I,aVL,V1-6ID < 0.0115 test accuracy (TA) were 81%, 84.8%, 82.3%, 84.8%, and 83.3%, respectively; the sensitivity (SE): 76.5%, 82.4%, 85.3%, 82.4%, and 76.9%; specificity (SP): 84.4%, 86.7%, 80%, 86.7%, and 87.5%; positive predictive values (PPV): 78.8%, 82.4%, 76.3%, 82.4%, and 80%; negative predictive values (NPV): 82.6%, 86.7%, 87.8%, 86.7%, and 85.4%; area under curve (AUC) values: 0.8922, 0.8794, 09016, 0.8824, and 0.8462 were respectively. These parameters of the novel ECG criteria were at least as good as those reported by other authors in the literature of the qualitative (TA: 67%, SE: 80%, SP: 34%, PPV: 75%, NPV: 42%, AUC: 0.57) and quantitative apical sparing (TA: 64-80%, SE: 66-81.3%, SP: 55-78.3%, PPV: 33-83.9%, NPV: 41-75%, AUC: 0.62-0.68) and left ventricular ejection fraction/global longitudinal strain >4.1 (TA: 77%, SE: 93%, SP: 38%, PPV: 79%, NPV: 69%, AUC: 0.65) echocardiographic criteria. Among the classical criteria, the low voltage in limb leads criterion was present most frequently (in 73.5%) in patients with CA, with slightly worse diagnostic value than the novel ECG criteria (TA: 78.5%, SE: 73.5%, SP: 82.2%, PPV: 75.8%, NPV: 80.4%).

CONCLUSIONS

The novel ECG criteria [mostly the aVR < 0.5, (I + aVR)/(V1-4) < 0.375] seem at least as reliable in the diagnosis of CA as the best echocardiographic myocardial deformation criteria and might be used either together with the echocardiographic criteria or as stand-alone criteria to diagnose CA in the future.

Lower Limit of Normality of Segmental Multilayer Longitudinal Strain in Healthy Adult Subjects

Speckle tracking echocardiography is an advanced imaging technique that allows for a more detailed assessment of cardiac global and regional function. Reference values for segmental longitudinal layered strain (subendocardial, mid-myocardial, and subepicardial) are scarce, limiting the clinical use of these measurements in clinical practice. Two hundred consecutive Caucasian healthy subjects (mean age = 37 ± 11 years) were enrolled in the study. The mean values of global longitudinal strain (GLS) for endocardial (Endo), mid-myocardial (Myo) and epicardial (Epi) layers were -22.9 ± 2.7, -20.0 ± 2.4 and -17.5 ± 2.1, respectively. The GLSEndo/GLSMyo ratio was 1.1 ± 0.05, while the GLSEndo/GLSEpi ratio was 1.3 ± 0.05. The apical strain-sparing ratio was >1 in 10% of the subjects (endocardium) and 7% (mid-myocardium). The lower limits for segmental LS were as follows: for endocardial LS, -10% (basal), -12% (mid), -14% (apical); for mid-myocardial LS, -10% -10% (basal), -10% (mid), -10% (apical); and for epicardial LS, -7% (basal), -8% (mid), -8% (apical). The findings of this study provide data regarding the lower limit of normality of LS for each LV segment and suggest, for practical considerations, that an LS value below 10% should be considered abnormal in any segment. Further larger studies are warranted to confirm these findings.