McConnell

McConnell's sign is a diagnostic finding observed in echocardiography, specifically in the context of evaluating patients for pulmonary embolism (PE). It is named after Dr. John C. McConnell who first described this echocardiographic feature in 1996. The sign is characterized by the presence of regional right ventricular dysfunction, with akinesia of the mid-free wall but normal motion at the apex. This pattern of motion is thought to be highly specific for acute pulmonary embolism, although it is not universally present in all cases.

Etiology and Pathophysiology

McConnell's sign arises from the acute pressure overload of the right ventricle (RV) that occurs in the setting of a significant pulmonary embolism. The obstruction of the pulmonary arteries increases pulmonary vascular resistance, leading to increased RV afterload. The RV, not accustomed to high pressure, dilates and struggles to maintain output. The apical segments of the RV are better perfused and may retain their function due to their more favorable blood supply, whereas the mid-free wall segments become akinetic due to ischemia or overstretching.

Clinical Significance

The presence of McConnell's sign on echocardiography can be a critical clue in the diagnosis of acute pulmonary embolism, especially in cases where the diagnosis is uncertain. It is important to note, however, that while highly specific, McConnell's sign is not highly sensitive for PE. This means that while its presence strongly suggests the diagnosis of PE, its absence does not rule out the disease. Therefore, McConnell's sign should be considered as part of a broader clinical assessment, including the evaluation of symptoms, risk factors, and other diagnostic tests such as D-dimer levels and computed tomography pulmonary angiography (CTPA).

Diagnosis

The diagnosis of McConnell's sign is made through echocardiography, a non-invasive imaging technique that uses ultrasound waves to create images of the heart. The echocardiogram will typically show hypokinesis or akinesis of the RV free wall, with sparing of the apical segments. This finding, in the appropriate clinical context, can support the diagnosis of acute pulmonary embolism.

Treatment and Prognosis

The treatment of a patient with a pulmonary embolism and McConnell's sign involves addressing the underlying PE. This typically includes anticoagulation therapy to prevent further clot formation, and in some cases, thrombolytic therapy to dissolve the existing clot. The prognosis of patients with PE and McConnell's sign depends on various factors, including the size and location of the embolus, the presence of underlying heart or lung disease, and the promptness of treatment initiation.

Conclusion

McConnell's sign, while not sensitive, is a specific echocardiographic finding for acute pulmonary embolism that reflects the unique pathophysiology of RV strain in this condition. Its recognition can aid in the timely diagnosis and management of patients with PE, highlighting the importance of echocardiography in the evaluation of patients with suspected acute pulmonary embolism.