Myocardial Contraction

IJCS

Editorial

Hyperthyroidism and Cardiac Contractility

Dhiãnah Santini de Oliveira Chachamovitz

Much information is lacking on hyperthyroidism and cardiac function, especially in isolated muscles. Certainly, the time the heart muscle is exposed to elevated thyroid hormones (TH) influences the magnitude of their effects. The primary changes seem to be related to increases in the heart mass/body mass ratio and in relaxation kinetics.

These cardiac changes may also be related not only to the time of exposure to excess thyroid hormones, but to the level or intensity of hyperthyroidism, as well as the underlying cardiac condition, which may reflect exercise conditioning and overload. In this sense, the cellular mechanisms of muscle adaptation, energy and oxygen consumption, certainly make differences. As well as muscle strength and sarcoplasmic/endoplasmic reticulum calcium (SRCa) activity, they may also have different individual adaptive characteristics.

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IJCS

Original Article

Effects of Hyperthyroidism on Contractility and Na+/Ca2+ Exchanger Activity in the Isolated Papillary Muscle of Rats

Angela Mara Rambo et al. João Victor Capelli Peixoto Rebeca Alves Lins de Albuquerque Ilana Kassouf Silva Rosalvo Tadeu Hochmueller Fogaça

Abstract

Background:

Hyperthyroidism (Hy) is an endocrine disorder, in which the thyroid hormones markedly alter the cardiac function. Increased myocardial contractility and cardiac output, improvement in diastolic relaxation, changes in electrical activity, increments in ventricular mass, and arrhythmias have been reported. However, the influences of thyroid hormones upon molecular mechanisms of cardiac functions have not yet been fully understood.

Objectives:

To evaluate changes in cardiac contractile parameters and the Na+/Ca2+ exchanger (NCX) function in induced hyperthyroid rats.

Methods:

Hy was induced by intraperitoneal injections of T3 (15 μg/100 g) for 10 days. Contractile parameters and NCX function were evaluated in the isolated papillary muscle. Data normality was confirmed by the Shapiro-Wilk test. The comparison between groups was performed through an unpaired Student’s t-test. Results are expressed as mean ± SD. The accepted significance level was p < 0.05.

Results:

Our data revealed, in the Hy group, an increase of 30.98% in the maximum speed of diastolic relaxation (–284.64 ± 70.70 vs. –217.31 ± 40.30 mN/mm2/sec (p = 0.027)) and a boost of 149% in the NCX function in late phase of relaxation (20.17 ± 7.90 vs. 50.22 ± 11.94 minutes (p = 0.002)), with no changes in the maximum twitch force (p = 0.605) or maximum speed of systolic contraction (p = 0.208) when compared to the control.

Conclusion:

The improvement in relaxation parameters is hypothetically attributed to an increase in Sarco-Endoplasmic Reticulum Ca2+ATPase isoform 2 (SERCA2) expression and an increased calcium flow through L-type channels that boosted the NCX function.

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IJCS

Editorial

Heart Failure – Pathophysiology and Current Therapeutic Implications

Mariana Vieira de Oliveira Bello et al. Fernando Bacal

The concept of translational medicine involves promoting the rapid transfer of observations made in the areas of research and pathophysiological understanding to the medical practice. This approach is a reality in major Brazilian research centers which link academia and clinical practice.

Heart failure (HF) is a complex syndrome that can manifest itself as heart failure with preserved ejection fraction (HFpEF), acute heart failure, or chronic heart failure with reduced ejection fraction (HFrEF). Here, we will cover the type of HF whose pathophysiology is understood the best and thus has disease-modifying treatments: HFrEF.

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IJCS

Editorial

Risk Scores for Stroke Prevention in Patients with Non-Valvular Atrial Prevention: Is it Time to Put Parameters of Left Atrial Appendage Morphology and Function Into Clinical Practice?

Angelo A. V. de Paola

Overall, one-third of thromboembolic events originated from the heart. Left atrial appendage (LAA) and its anatomic complexity has been implicated in 90% of cases of thrombus formation and cardioembolic events in patients with non-valvular atrial fibrillation (AF). Risk scores to predict thromboembolism from AF, such as CHADS₂ and CHA₂DS₂VASc are widely used to guide anticoagulation therapy and varies in relation to comorbidities associated with the thrombogenic substrate; however, because of its clinical conception, they did not include atrial anatomy (atrial enlargement), function (flow velocities) and electrophysiology (atrial fibrillation burden). Patients with CHA₂DS₂VASc score ≥ 2 are at intermediate or higher risk (event rate ≥ 2-3%/year) and anticoagulation is recommended. Left atrial variables such as LAA function and morphology, routinely studied by transesophageal echocardiography (TEE), were not considered in these scores.

In 2012, Di Biase et al.; published a retrospective study of 932 patients with AF and computed tomography (CT)/magnetic resonance imaging (MRI) classification of four different types of LAA morphologies: chicken wing, cactus, windsock and cauliflower. Non-chicken wing categories were 4 to 8 times more likely to have had stroke/TIA. Eight additional cross-sectional studies utilizing this classification for LAA morphology in 2,210 patients (6 with CT and 2 with TEE), found a significant association with non-chicken-wing morphology and stroke in 5 series^– and no significant difference in 3 other studies.^–

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Original Article

Association between Morphodynamic Variables by Transesophageal Echocardiography and CHA2DS2-Vasc Values

Renata Rejane Linhares et al. Dalmo Antonio Ribeiro Moreira Luciana Braz Peixoto Andresa Paes da Cruz … Luara Piovam Garcia Rodrigo Bellio de Mattos Barretto David Costa de Souza Le Bihan Carlos Eduardo Suaide Silva

Abstract

Background:

In atrial fibrillation (AF), the CHA₂DS₂-VASc score calculates the risk for stroke. Di Biase classified the left atrial appendage (LAA), using magnetic resonance imaging, into 4 morphological types and correlated it with cerebrovascular events. Transesophageal echocardiography (TEE) also evaluates LAA and is a more widespread technique.

Objective:

To evaluate, using TEE, the possibility of characterizing LAA and to analyze its morphological aspects using the CHA₂DS₂VASc score.

Methodology:

A total of 247 patients were divided into three groups considering the CHA₂DS₂-VASc score: Group 1: 0 and 1; Group 2: 2 and 3 and, Group 3: ≥ 4 points. TEE produced the echocardiographic data. LAA was classified into thrombogenic and non-thrombogenic morphologies. In the analysis of statistical tests, a significance level of 5% was adopted.

Results:

The average age was 50 and 16.2% presented AF. In Group 1, we observed normal variables with a lower prevalence of AF (8.7%, p < 0.001). In group 2, spontaneous contrast was detected in 26.7%, (p < 0.001), thrombus in 6.7% (p = 0.079) and flow velocity in LAA < 0.4 m/s in 22.7% (p < 0.001) of the cases. Group 3 presented the highest percentages of AF (31.8%, p < 0.001), stroke/TIA (77.3%, p < 0.001), EF < 55% (18.2%, p = 0.010) and higher prevalence of thrombogenic type LAA (72.7%, p = 0.014). A higher occurrence of stroke/TIA was observed in patients with thrombogenic LAA (25.2%) compared to the non-thrombogenic group (11.2%), (p = 0.005).

Conclusions:

The thrombogenic morphology of LAA identified in TEE presented a higher risk of stroke regardless of the CHA₂DS₂VASc score. Patients with higher scores had greater abnormalities in echocardiographic variables.

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Hyperthyroidism and Cardiac Contractility

Effects of Hyperthyroidism on Contractility and Na+/Ca2+ Exchanger Activity in the Isolated Papillary Muscle of Rats

Abstract

Background:

Objectives:

Methods:

Results:

Conclusion:

Heart Failure – Pathophysiology and Current Therapeutic Implications

Risk Scores for Stroke Prevention in Patients with Non-Valvular Atrial Prevention: Is it Time to Put Parameters of Left Atrial Appendage Morphology and Function Into Clinical Practice?

Association between Morphodynamic Variables by Transesophageal Echocardiography and CHA2DS2-Vasc Values

Abstract

Background:

Objective:

Methodology:

Results:

Conclusions:

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