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Biomedical subjects

John E Madias

Publications and source records attributed to John E Madias.

At least 19 recordsLinked to original sources
PubMed2006

Acute anterior myocardial infarction followed by acute inferoposterior myocardial infarction: the case of the necrotic QRS counterpoise.

A case of a 55-year-old man who suffered an acute anterior myocardial infarction (MI) followed by an acute inferoposterior MI 1 month later, which led to his demise from cardiogenic shock, is presented. The electrocardiogram after his second MI resulted in profound decrease in the amplitude of the QRS complexes and cancellation of the features of the previous anterior MI (necrotic QRS counterpoise). The implications of these electrocardiogram alterations, particularly when using this modality in QRS scoring systems for estimation of infarct size or left ventricular function, are discussed.

Electrocardiography↗
PubMed2006

P-wave and QRS complex measurements in patients undergoing hemodialysis.

Hemodialysis (HD) has been associated with an increase in the amplitude of QRS complexes. Experience in a single patient with multiple measurements has shown that HD leads also to augmentation of P-wave amplitude. The objective of this investigation was to evaluate electrocardiogram (ECG) changes with HD in a cohort of patients undergoing this procedure with particular emphasis on the P-wave and QRS complex changes. The sum of amplitudes of P waves (OP) and QRS complexes (OQRS) in millimeters in the 12 leads of the ECG, along with a host of other ECG parameters, body weight, blood pressure, heart rate, electrolytes, and hemoglobin/hematocrit were measured before and immediately after HD in 47 patients. Hemodialysis resulted in a loss of a mean of 3 kg of weight and an increase in the SigmaP, SigmaQRS, mean QRS duration, maximum P-wave duration, and P-wave duration measured in lead II, whereas the changes in mean P-wave and corrected QT interval durations were not statistically significant. Percentage change (Delta%) in SigmaP and SigmaQRS correlated poorly with Delta% in electrolytes, hematocrit, blood pressure, heart rate, and weight. Values for SigmaP and SigmaQRS vs weight were r = 0.105, P = .48 and r = 0.09, P = .51, respectively. The Delta% in SigmaP correlated well with Delta% in SigmaQRS (r = 0.42, P = .003). Alterations in P-wave amplitudes and duration commensurate with the ones affecting the corresponding QRS complexes occur in patients undergoing HD and indicate that evaluation of measurements in serial ECGs should take this into account. The mechanisms of these phenomena continue to be elusive, and whether they represent cardiac and/or extracardiac influences has not as yet been unraveled.

Adult↗
PubMed2006

Reversible attenuation of voltage of QRS complexes and P waves and shortening of QRS duration and QTc interval consequent to large perioperative intravenous fluid infusions.

A 39-year-old woman with a gangrenous pyelonephritis and septic shock underwent a nephrectomy, in preparation for which, she received large preoperative fluid resuscitation. Quantitative evaluation of her serial standard electrocardiograms (ECGs) revealed reversible attenuation of voltage in association with peripheral edema (PERE), with the latter being eventually completely abolished. The transient low-voltage ECG (LVECG) (attenuated amplitudes of QRS complexes) was associated with parallel transient attenuation of the amplitude of P waves and shortening of the QRS duration and QTc, whereas the P-wave duration increased. Awareness of these ECG changes with PERE of varying pathophysiologic mechanisms is useful, ensuring avoidance of improper procedural and laboratory testing and correct measurement of wave amplitudes and ECG time intervals for proper ECG diagnosis. In addition, these ECG associations can be used as indices of the presence and course of PERE postoperatively, as well as in a large variety of medical settings.

Adult↗
PubMed2006

Discordance of diagnosis of ventricular aneurysm made by the electrocardiogram and myocardial imaging: "ST-segment counterpoise" as a hypothetical mechanism.

There is a discordance between ECG and imaging modalities in the diagnosis of ventricular aneurysm (VA) consequent to an old myocardial infarction. A hypothesis is being proposed that this discordance, which results in electrocardiograms (ECGs) not showing ST-segment elevations (+ST) in patients with proven by imaging modalities to have VA (false negative, low diagnostic sensitivity), may be due to "ST-segment counterpoise," rendering the ECG isoelectric. Accordingly, +ST generated by myocardial territories involved with the VA, when poised opposite each other, cancel out via vectorial summation, rendering the ECG falsely negative for VA. Also, a misalignment of the apex longitudinal axis with the left ventricular inflow axis due to myocardial remodeling from the VA (boot-shaped heart) when the apex and another myocardial region are involved with VA leads to +ST cancellation and a false-negative ECG for VA. ST-segment counterpoise as a mechanism rendering the ECG falsely negative for VA can be tested in the future if studies of patients with VA adopt in their methodologies a systematic reporting of severity and topography [corrected] of the regional left ventricular contraction abnormalities, as recommended by the American Society of Echocardiography.

Arrhythmias, Cardiac↗
PubMed2005

Comparability of the standing and supine standard electrocardiograms and standing sitting and supine stress electrocardiograms.

The aim of this study was to evaluate whether change in the patients' position during the electrocardiogram (ECG) recording alters the various components of the ECG curve. Concerns whether ECGs in medically compromised patients recorded in a sitting position should be considered "standard" tracings and whether ECGs recorded in the supine and standing positions and ECGs recorded in different positions in the Exercise Laboratory are interchangeable provided the impetus for this study. The ECG was recorded in the supine and standing positions in 10 patients using standard electrode placement and in the sitting, standing, and supine positions in 16 patients using the Mason-Likar electrode system. Comparisons of sums of P waves and QRS complexes of various combinations of ECG leads from recordings in different positions and amplitudes of Q, R, and S waves of all 12 ECG leads revealed stability in the standard and stress ECGs, although few statistically significant but minor changes were noted in some comparisons, which, however, could not be expected to have any diagnostic significance. Comparison of standard ECGs recorded in patients in the supine and standing positions and stress ECGs recorded in the sitting, standing, and supine positions are interchangeable; this should allay concerns about recording the standard ECG in unconventional positions and may facilitate and make more cost-effective ECG recording in busy outpatient clinic environments.

Electrocardiography↗
PubMed2005

The impact of changing oedematous states on the QRS duration: implications for cardiac resynchronization therapy and implantable cardioverter/defibrillator implantation.

Increased ECG QRS duration (QRSd) in patients with dilated cardiomyopathy (DCM) or heart failure (HF) is a well-known phenomenon. The QRSd is not a static ECG measurement but shows fluctuations, and its recent inclusion among the parameters used in referring patients for implantable cardioverter/defibrillators (ICDs) or cardiac resynchronization therapy (CRT) has led to renewed interest in its natural course and its determinants. Although clinical deterioration has been traditionally associated with increasing QRSd, its changes often are left unexplained. Also, the recent description of a decrease in QRSd, well correlated with attenuated amplitude of QRS complexes in patients with peripheral oedema (PERO) in the context of a variety of illnesses, has added complexity to the matter. This communication aims at calling attention to the importance of a few clinical and ECG parameters when documenting changes in the QRSd in serial ECGs. Thus, presence or absence of PERO and change in the patients' weight, along with alteration in the amplitude of QRS complexes and shifts to/from incomplete/complete bundle branch block patterns, all should be considered when assessing changes in QRSd for meaningful follow-up of patients with DCM or CHF, or referral for ICD or CRT. Evaluation of the QRSd as a selection parameter for referring patients suitable for device implantation should continue along with the employment of mechanical analysis of ventricular dyssynchrony. Although reference here is made to QRSd particularly in connection with DCM and HF, the above apply to other oedematous states (i.e. patients with chronic renal failure, or those undergoing haemodialysis).

Cardiac Pacing, Artificial↗