Low Voltage With Pericardial Effusion

In this issue of CHEST, Japan’s leading investigator of pericardial disease, Tetsuro Sugiura, MD, and his colleagues contribute a unique report of patients free of heart disease with asymptomatic pericardial effusions, small to large, some of whom had PR segment and ST-T wave changes. The report raises as many questions as it answers, and these will require further investigation. By standard definition, 32 of 121 patients had low voltage QRS. In the entire group, widespread ST-segment elevation was found in only 8 patients, and widespread PR-segment depression in 32 patients. PR-segment depressions were significantly more frequent in those with low QRS voltage than in those free of low voltage (more cases may have escaped detection when low voltage applied to more than the QRS complexes). The authors appropriately lumped moderate and large pericardial effusions, as it has been shown that the physiologic effect—increased ventricular interaction of even asymptomatic effusions was similar in moderate-to-large effusions as opposed to small effusions.

Eight of 32 patients with PR-segment deviations had ST-segment deviations, while none with isoelectric PR segments had ST deviations, and significantly more patients with isoelectric PR segments had moderate-to-large effusions than small effusions. Small voltage and PR-segment deviations were rare in patients who had clinically silent pericardial effusions with an unsurprising trend to lower voltage in moderate-to-large effusions.

Certain findings are relatively remarkable: all patients with PR deviations had either a malignancy or a connective tissue disease. In contrast, it is not surprising that all patients with hypothyroidism and with renal disease had no ECG changes.

The authors conclude that there is subepicardial myocardial involvement by inflammation that they believe can cause low voltage despite small effusions and conclude “even a small but inflammatory effusion can cause low voltage in the presence of PR-segment depressions.” They thus assume the fluid to be inflammatory and, presumably because the patients were asymptomatic, they assumed that neither drainage nor biopsy was indicated. In this connection, no patients had tamponade, and Sugiura and colleagues did not describe any of the large effusions as massive. PR-segment deviations can be safely attributed to early appearance of the atrial T wave because they are always opposite to the direction of the P wave with an appropriate spatial vector. However, it is not certain that all PR-segment deviations must be inflammatory.

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