Paroxysmal dyspnea
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Paroxysmal Dyspnea: Definition and Clinical Presentation
Paroxysmal dyspnea refers to sudden, episodic attacks of shortness of breath that can be distressing and often occur at rest or during the night. These episodes are commonly seen in patients with underlying cardiac or respiratory conditions, but can also arise from less typical causes 38.
Cardiac Causes of Paroxysmal Dyspnea
Myocardial Ischemia and Coronary Artery Disease
In patients with stable coronary artery disease (CAD), paroxysmal dyspnea can be caused by transient myocardial ischemia. Studies show that about 35% of patients with stable CAD and paroxysmal dyspnea have evidence of myocardial ischemia, which can be predicted using clinical features, ECG, and echocardiography 27. However, myocardial ischemia is often not the sole cause; many patients have multiple contributing factors such as heart failure, valvular disease, obesity, anxiety, and pulmonary disorders 7.
Heart Failure and Cardiac Asthma
Paroxysmal dyspnea is a classic symptom of heart failure, particularly left-sided heart failure. The attacks often occur at night (paroxysmal nocturnal dyspnea) and are linked to fluid shifts when lying down, which increase the workload on the heart and can precipitate acute episodes of breathlessness 38. This mechanism is sometimes referred to as "cardiac asthma," and is distinguished from pulmonary asthma by its cardiac origin and association with heart disease 8.
Valvular Disease and Syphilitic Aortitis
Aortic insufficiency, especially when caused by syphilitic aortitis, is frequently associated with paroxysmal dyspnea. In these cases, the symptom may be the first sign of the underlying disease, particularly when the lesion is at the root of the aorta 6. Paroxysmal dyspnea is rarely seen with aortic insufficiency of rheumatic origin, highlighting the importance of etiology in diagnosis 6.
Cardiorenal Syndrome
Paroxysmal dyspnea is also observed in patients with advanced heart and kidney disease, a condition known as cardiorenal syndrome. The interplay between cardiac and renal dysfunction can exacerbate fluid overload and contribute to episodes of acute breathlessness 4.
Non-Cardiac and Unusual Causes
Neurological Disorders
In rare cases, paroxysmal dyspnea can occur in patients with neurological conditions such as Parkinson's disease. These episodes are not always explained by anxiety, respiratory muscle rigidity, or medication side effects, and may represent a distinct, under-recognized symptom in this population 1.
Abdominal and Other Uncommon Causes
Occasionally, paroxysmal dyspnea may be caused by non-cardiac and non-pulmonary conditions, such as large abdominal masses. For example, a splenic tumor causing left-sided pleural effusion led to paroxysmal dyspnea in one reported case, demonstrating the need for thorough evaluation when common causes are excluded 5.
Mechanisms and Triggers
Fluid Shifts and Postural Hemodilution
Nocturnal attacks of paroxysmal dyspnea are often linked to fluid shifts that occur when a person lies down. This increases blood volume returning to the heart, which can precipitate acute left-sided heart failure in susceptible individuals 3. Patients with low plasma proteins may be more prone to severe attacks due to these physiological changes 3.
Multiple Contributing Factors
It is common for patients to have more than one cause for their dyspnea. Combinations of heart failure, ischemia, valvular disease, obesity, anxiety, and pulmonary disorders are frequently observed, making diagnosis and management complex 7.
Conclusion
Paroxysmal dyspnea is a multifactorial symptom most often associated with cardiac conditions such as heart failure, myocardial ischemia, and valvular disease, but can also arise from neurological disorders or rare non-cardiac causes. Accurate diagnosis requires careful clinical assessment and consideration of multiple potential contributing factors, as many patients have more than one underlying cause for their symptoms 12345678.
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