What is one of the main causes of premature junctional contractions (PJCs)?

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Premature junctional contractions (PJCs) are characterized by an early beat originating from the junctional tissue, or the area around the atrioventricular (AV) node, rather than from the atria or ventricles. One of the main causes of PJCs is increased automaticity of junctional pacemaker cells. This means that these cells become more excitable and can depolarize spontaneously, resulting in the early contractions that are characteristic of PJCs. Factors that can lead to increased automaticity include various physiological conditions and irritations to the cardiac tissue.

The other options, while they may contribute to broader cardiac issues, are not directly implicated in the occurrence of PJCs as primary causes. For example, hypertension, ventricular hypertrophy, and coronary artery disease could affect overall heart function and rhythm, but do not specifically lead to the increased automaticity of junctional pacemaker cells that is directly responsible for PJCs.