An analysis of the electrocardiogram QT interval

No reports testing the efficacy of the use of the QT/RR ratio <1/2 for detecting a normal QTc interval were found in the literature. The objective of the present study was to determine if a QT/RR ratio <=1/2 can be considered to be equal to the normal QTc and to compare the QT and QTc measured and calculated clinically and by a computerized electrocardiograph. Ratios (140 QT/RR) of 28 successive electrocardiograms obtained from 28 consecutive patients in a tertiary level teaching hospital were analyzed clinically by 5 independent observers and by a computerized electrocardiograph. The QT/RR ratio provided 56 percent sensitivity and 78 percent specificity, with an area under the receiver operator characteristic curve of 75.8 percent (95 percentCI: 0.68 to 0.84). The divergence in QT and QTc interval measurements between clinical and computerized evaluation were 0.01 ± 0.03 s (95 percentCI: 0.04-0.02) and 0.01 ± 0.04 s (95 percentCI: -0.05-0.03), respectively. The QT and QTc values measured clinically and by a computerized electrocardiograph were similar. The QT/RR ratio <=1/2 was not a satisfactory index for QTc evaluation because it could not predict a normal QTc value.

An analysis of the electrocardiogram QT interval.

No reports testing the efficacy of the use of the QT/RR ratio <1/2 for detecting a normal QTc interval were found in the literature. The objective of the present study was to determine if a QT/RR ratio < or =1/2 can be considered to be equal to the normal QTc and to compare the QT and QTc measured and calculated clinically and by a computerized electrocardiograph. Ratios (140 QT/RR) of 28 successive electrocardiograms obtained from 28 consecutive patients in a tertiary level teaching hospital were analyzed clinically by 5 independent observers and by a computerized electrocardiograph. The QT/RR ratio provided 56% sensitivity and 78% specificity, with an area under the receiver operator characteristic curve of 75.8% (95%CI: 0.68 to 0.84). The divergence in QT and QTc interval measurements between clinical and computerized evaluation were 0.01 +/- 0.03 s (95%CI: 0.04-0.02) and 0.01 +/- 0.04 s (95%CI: -0.05-0.03), respectively. The QT and QTc values measured clinically and by a computerized electrocardiograph were similar. The QT/RR ratio < or =1/2 was not a satisfactory index for QTc evaluation because it could not predict a normal QTc value.

[Etiology of left bundle branch block in Porto Alegre]. / Estudo da etiologia do bloqueio do Ramo Esquerdo em Porto Alegre.

PURPOSE: To determine the type of cardiac disease causing left bundle branch block (LBBB) in Porto Alegre, Brazil, and to assess the role of associated left axis deviation (-30 degrees or more in the frontal plane) in order to identify a specific etiology of LBBB. METHODS: Through reports from the assistant physicians or through examination of the patients, the underlying heart disease in 264 cases of LBBB was assessed. The chi-square test was used to determine a possible association between left anterior hemiblock LBBB and one or more specific type of underlying heart disease. RESULTS: Systemic arterial hypertension (30.7%), ischemic heart disease (30.3%), valvar heart disease (8.7%), cardiomyopathies (7.5%), idiopathic degenerative disease of the conduction system (1.6%) and miscellaneous heart diseases (1.2%) were the underlying heart diseases. The presence of LBBB did not indicate any specific type of cardiac disease. CONCLUSION: The causes of LBBB in Porto Alegre are the same as reported in the international medical literature. Upward and leftward deviation (> or = -30 degrees) of QRS axis in the frontal plane did not show statistical significant association with any type of underlying cardiac disease.

[Evaluation of QRS voltage in 12 derivations and Cornell criteria in the diagnosis of left ventricular hypertrophy]. / Estudo da voltagem do QRS em 12 derivações e do critério Cornell na detecção de hipertrofia ventricular esquerda.

PURPOSE: To search for the existence and degree of correlation between total 12 lead ECG amplitude and the sum of RaVL + SV3 > 28 mm (for men) or > 20mm (for women) and left ventricular hypertrophy (LV mass calculated by echocardiography > 215g for both sexes). METHODS: ECG and echocardiograms of 227 consecutive patients were examined and submitted to statistical analysis searching for correlation between total 12 lead ECG amplitude and Cornell criteria and LV mass (ASE formula modified by Devereux). RESULTS: Patients had ischemic heart disease, hypertension, valvular disease, cardiomyopathy or other less common heart diseases, or had no cardiac illness at all. There was statistically significant association of total 12 lead amplitude > 120mm and Cornell criteria with LV mass > 215g (p = 0.02 and p = 0.01 respectively). Total ECG amplitude showed 74.3% sensitivity, 42.6% specificity, and 52.4% accuracy. Cornell criteria showed values of 37.8%, 82.7% and 68.7% respectively. CONCLUSION: Total 12-lead amplitude presented limited diagnostic performance for detecting LV hypertrophy, as well as did ECG Cornell criteria, although the latter was more specific and more accurate.

Hipertensao arterial sistemica essencial. Aspects da deteccao e manejo. / Systemic essential arterial hypertension. Aspects of the detection and management

Os autores fazem breves comentarios sobre alguns aspectos praticos de deteccao e do manejo da hipertensao arterial sistemica essencial

Ventriculografia radioisotopica en repouso e durante esforço: valores normais / Radioisotopic ventriculography at rest and during effort: normal values

A ventriculografia radioisotopica e uma tecnica de medicina nuclear que vem sendo utilizada, particularmente no diagnostico da doenca coronaria. A maior sensibilidade e especificidade deste metodo, em relacao a eletrocardiografia de esforco, ja foi estabelecida. Esta tecnica avalia a funcao ventricular esquerda em repouso e durante esforco, a partir da administracao de um tracador radioativo (99m Tc-hemacia) que permanece no compartimento vascular. Para melhor valorizar a resposta ventricular ao esforco nos pacientes com coronariopatia, foram determinados os valores normais em nosso servico. Estudaram-se 20 voluntarios, sem evidencia clinica de cardiopatia e com teste ergometrico normal. Todos submeteram-se a um exercicio adequado (produto da frequencia cardiaca pela pressao arterial sistolica superior a 25000) sendo obtida uma fracao de ejecao media do ventriculo esquerdo em repouso de 54,1% + ou - 6,1% e durante exercicio, de 65,6% + ou - 7,6%. A variacao com o esforco atingiu 21,3% + ou - 8,9%. Os resultados, no grupo masculino, estao em concordancia com os apresentados por outros investigadores, os quais nao relatam um numero significativo de estudos em mulheres. O grupo feminino apresentou valores da fracao de ejecao significativamente inferiores aos dos homens-repouso (p < 0,05) e esforco (p<0,01) sendo, no entanto, as variacoes porcentuais entre os resultados de repouso e esforco similares (NS) entre os sexos