心磁図法による右室負荷の診断

Diagnosis of right ventricular overloading by means of the magnetocardiography

　右室負荷の診断に，従来から心電図法が広く用いられているが，その診断率は高くない。

　心磁図法^1）は，心起電力により作られる磁界の記録であるが，磁界は電場とは異なる物理学的特性があるため，心電図法では診断できない右室負荷を診断できる可能性がある。著者らは，右室負荷診断における心磁図法の有用性を検討するために本研究を行った。

Magnetocardiograms (MCG) were recorded by means of a second-derivative SQUID (superconduc-ting quantum interference device) magnetometer at 36 points on the anterior chest wall in 30 normal subjects and 37 cases with various diseases which might cause right ventricular overloading to deter-mine the clinical value of the MCG as compared to the standard electrocardiograms (ECG).

Following MCG criteria for the diagnosis of right ventricular overloading were proposed based on the normal data.

①RB_-2≧15×10^-8 gauss ②SF_-3≧4×10^-8 gauss Right ventricular overloading was diagnosed if one of the above criteria was met.

RB_-2, SF_-3 and RB_-2+SF_-3 showed significant posi_tive correlations with the systolic pressures of the pulmonary artery or the right ventricle. Diagnostic reliability of the MCG and ECG were evaluated in 35 normal subjects and 16 cases with various diseases which might cause right ventricular overloading whose systolic pressure of the pulmonary artery or the right ventricle exceeded 30 mmHg.

Sensitivity and specificity of the MCG were 73. 3% and 94. 8%, and those of the ECG were 31. 2% and 94. 2% respectively. Specificity increased up to 100%, but sensitivity remained low at 31.2% when modified Roman's criteria in which R/S V₁≧2 was used instead of≧1, were applied.

Positivities of the MCG and ECG criteria were compared in 37 cases of various diseases which might cause right ventricular overloading. Diagnosis by both methods agreed in 62%. There were 15 cases (40.5%), in which MCG criteria were met, but ECG criteria were not met. There was no cases in which ECG criteria were met, but MCG criteria were not met.

These results suggested usefulness of the MCG for the diagnosis of right ventricular overloading.