Basha, Nabel Rajab

Premature ventricular contractions (PVCs) are common arrhythmia encountered in patients with and without structural heart disease. Although often benign and asymptomatic, they may also cause palpitations, exercise intolerance, presyncope, and reduced quality of life, and in some patients can contribute to PVC-induced cardiomyopathy or trigger malignant ventricular arrhythmias. Their clinical significance depends on symptom burden, PVC frequency, ventricular function, and the presence of underlying myocardial disease. Diagnostic evaluation includes electrocardiography, ambulatory rhythm monitoring, echocardiography, exercise testing, and cardiac magnetic resonance imaging for tissue characterization and risk stratification. Management ranges from reassurance and lifestyle modification to pharmacologic therapy and catheter ablation. Beta-blockers and nondihydropyridine calcium channel blockers remain common first-line options, whereas antiarrhythmic drugs may be considered in carefully selected patients. Catheter ablation is an effective treatment for symptomatic PVCs, high PVC burden, and PVC-induced cardiomyopathy, with high procedural success rates and favorable effects on arrhythmic burden and ventricular function. Novel approaches, including electrocardiographic imaging-guided planning, pulsed field ablation, stereotactic radioablation, neuromodulation, and renal denervation, may further expand future therapeutic options. This review summarizes the pathophysiology, clinical implications, diagnostic evaluation, and contemporary management of PVCs, with emphasis on medical therapy, catheter ablation, and emerging treatments.

Coronary microvascular dysfunction (CMD) is increasingly recognized as a central mechanism underlying myocardial ischemia, heart failure with preserved ejection fraction, and adverse cardiovascular outcomes in patients with and without obstructive coronary artery disease. The coronary microcirculation plays a critical role in regulating myocardial perfusion through tightly coordinated myogenic, metabolic, and endothelial pathways. Disruption of these mechanisms results in impaired vasodilatory capacity, abnormal coronary flow reserve, and microvascular ischemia. This review summarizes the anatomy and physiology of coronary microcirculation and examines the pathophysiologic mechanisms driving CMD, including endothelial dysfunction, structural remodeling, inflammation, and neurohormonal dysregulation. Contemporary diagnostic strategies are reviewed, with emphasis on invasive coronary function testing and advanced noninvasive imaging modalities such as positron emission tomography and cardiac magnetic resonance imaging. The clinical implications of CMD across diverse disease states, including ischemia with nonobstructive coronary arteries, heart failure, and cardiomyopathies, are discussed. Finally, current therapeutic approaches, prognostic considerations, and emerging research directions aimed at improving diagnosis and targeted treatment of CMD are highlighted.

Coronary artery spasm (CAS) is a dynamic vasomotor disorder characterized by transient, intense constriction of epicardial coronary arteries, leading to myocardial ischemia in patients with and without obstructive coronary artery disease. CAS plays a central role in vasospastic angina, ischemia with nonobstructive coronary arteries and myocardial infarction with nonobstructive coronary arteries, malignant arrhythmias, and sudden cardiac death. Its pathophysiology is multifactorial, involving endothelial dysfunction, vascular smooth muscle hyperreactivity, inflammation, oxidative stress, autonomic imbalance, and genetic susceptibility, with notable ethnic and sex-related differences. Diagnosis relies on integration of clinical features, electrocardiographic changes, and invasive coronary provocation testing using acetylcholine or ergonovine, supported by advanced imaging and functional assessment when microvascular involvement is suspected. Management is centered on calcium channel blockers and nitrates, aggressive risk factor modification, particularly smoking cessation, and individualized strategies for refractory or high-risk patients. Improved recognition and standardized diagnostic pathways are essential to optimize outcomes and reduce life-threatening complications associated with CAS.

Shock is a life-threatening state of circulatory failure characterized by inadequate tissue oxygen delivery and cellular hypoxia. Lactate has emerged as a central biomarker in the diagnosis, risk stratification, and management of shock, yet its interpretation is complex and context dependent. Although traditionally viewed as a marker of anaerobic metabolism and tissue hypoperfusion, hyperlactatemia in distributive shock, particularly sepsis, frequently reflects multifactorial mechanisms, including increased aerobic glycolysis, adrenergic stimulation, mitochondrial dysfunction, and impaired hepatic clearance. This review examines the pathophysiology and classification of shock, the biochemical basis of lactate production and clearance, and the prognostic significance of both static lactate levels and lactate kinetics. We synthesize evidence supporting lactate as a robust prognostic marker while highlighting limitations of lactate-targeted resuscitation strategies. Emerging data favor multimodal approaches integrating lactate trends with complementary perfusion markers such as capillary refill time and central venous oxygen saturation. Lactate should be interpreted as one component of a comprehensive physiological assessment rather than an isolated therapeutic target.