Correlation between changes in R wave amplitude and left ventricular volume induced by rapid atrial pacing

Respiratory Variations in Electrocardiographic R-Wave Amplitude during Acute Hypovolemia Induced by Inferior Vena Cava Clamping in Patients Undergoing Liver Transplantation

The aim of this study was to analyze whether the respiratory variation in electrocardiogram (ECG) standard lead II R-wave amplitude (ΔRDII) could be used to assess intravascular volume status following inferior vena cava (IVC) clamping. This clamping causes an acute decrease in cardiac output during liver transplantation (LT). We retrospectively compared ΔRDII and related variables before and after IVC clamping in 34 recipients. Receiver operating characteristic (ROC) curve and area under the curve (AUC) analyses were used to derive a cutoff value of ΔRDII for predicting pulse pressure variation (PPV). After IVC clamping, cardiac output significantly decreased while ΔRDII significantly increased (p = 0.002). The cutoff value of ΔRDII for predicting a PPV >13% was 16.9% (AUC: 0.685) with a sensitivity of 57.9% and specificity of 77.6% (95% confidence interval 0.561 – 0.793, p = 0.015). Frequency analysis of ECG also significantly increased in the respiratory frequency band (p = 0.016). Although significant changes in ΔRDII during vena cava clamping were found at norepinephrine doses <0.1 µg/kg/min (p = 0.032), such changes were not significant at norepinephrine doses >0.1 µg/kg/min (p = 0.093). ΔRDII could be a noninvasive dynamic parameter in LT recipients presenting with hemodynamic fluctuation. Based on our data, we recommended cautious interpretation of ΔRDII may be requisite according to vasopressor administration status.

R-wave amplitude in lead II of an electrocardiograph correlates with central hypovolemia in human beings

OBJECTIVES

Previous animal and human experiments have suggested that reduction in central blood volume either increases or decreases the amplitude of R waves in various electrocardiograph (ECG) leads depending on underlying pathophysiology. In this investigation, we used graded central hypovolemia in adult volunteer subjects to test the hypothesis that moderate reductions in central blood volume increases R-wave amplitude in lead II of an ECG.

METHODS

A four-lead ECG tracing, heart rate (HR), estimated stroke volume (SV), systolic blood pressure, diastolic blood pressure, and mean arterial pressure were measured during baseline supine rest and during progressive reductions of central blood volume to an estimated volume loss of >1,000 mL with application of lower-body negative pressure (LBNP) in 13 healthy human volunteer subjects.

RESULTS

Lower-body negative pressure resulted in a significant progressive reduction in central blood volume, as indicated by a maximal decrease of 65% in SV and maximal elevation of 56% in HR from baseline to -60 mm Hg LBNP. R-wave amplitude increased (p < 0.0001) linearly with progressive LBNP. The amalgamated correlation (R2) between average stroke volume and average R-wave amplitude at each LBNP stage was -0.989.

CONCLUSIONS

These results support our hypothesis that reduction of central blood volume in human beings is associated with increased R-wave amplitude in lead II of an ECG.

Augmentation of the amplitude of electrocardiographic QRS complexes immediately after hemodialysis: a study of 26 hemodialysis sessions of a single patient, aided by measurements of resistance, reactance, and impedance

An increase in the amplitude of electrocardiogram QRS complexes ( upward arrow QRS) with hemodialysis (HD) has been invariably documented, but the relationship with weight loss has varied, and other parameters (ie, hemoglobin, body electrical properties), which could be determinants of upward arrow QRS, have not all been evaluated in the same patients. We investigated a patient immediately before and after 26 sessions of HD with measurements of a host of variables. Statistically significant correlations were found only between weight loss and net fluid removed (r =.72, P =.0005), and percentage change in the sums of QRS complexes of all 12-electrocardiogram leads and weight lost during HD (r =.41, P =.038). HD imparts a reproducible upward arrow QRS, but variation in all the other intercorrelations can be attributed to the complexity of the procedure and its variable impact on many body parameters.

Diminution of QRS complexes caused by anasarca after an acute myocardial infarction: a case report and a discussion of the plausible underlying pathophysiological mechanisms

We describe the case of an 81-year-old man with an acute anterior myocardial infarction (MI), complicated by anoxic encephalopathy, respiratory, and acute renal failure, who developed gradually marked reduction in the QRS complexes of his electrocardiogram (ECG) in the process of gaining 44 pounds, due to anasarca. Such ECG pattern has been recently associated with marked peripheral edema in the context of critical illness of varying etiologies. Our patient did not have a pericardial effusion, and his gradually increasing weight values correlated strongly with the corresponding sums of the amplitudes of the QRS complexes of the 12-lead ECGs (r =.92, P =.0029). The mechanism of this ECG phenomenon is attributed to a reduction of the overall transfer impedance of the conducting volume surrounding the heart, which leads to an attenuation of the potentials recorded on the body surface, due to a shunting effect of the edematous subcutaneous connective tissues. This reduction of the composite transfer impedance of the conducting medium is being mediated by the low resistivity of the water of the retained anasarca fluid.

Demonstration of the relationship between heart dimensions and QRS voltage amplitude

This study was undertaken to elucidate the still debated question of the relationship between cardiac volume and QRS voltage amplitude. The authors studied 14 healthy men, aged 24-61 years (mean age, 41.2 +/- 12.1 years). They underwent a reduction in venous return, produced by simultaneously inflating sphygmomanometric cuffs placed around the most proximal portion of each of the four limbs. In basal conditions and 5 minutes after cuff inflation, two-dimensional and M-mode echocardiograms were recorded with vectorcardiographic loops and scalar Frank leads. The reduction of the venous return to the heart induced a significant decrease of the end-diastolic left ventricular diameter (from 52.4 +/- 4.2 to 48.5 +/- 4.6 mm, P < .001), of the R wave amplitude in leads X and Y, of the sum of the R wave amplitudes in the three leads,and of the maximal vector in the frontal and horizontal planes. No significant changes in the heart rate or arterial blood pressure were observed. These results support Brody's theory concerning the relationship between cardiac blood volume and QRS voltage.

Exercise-induced changes in R wave amplitude and heart rate in normal subjects

An intermittent exercise protocol on a treadmill was used to examine six healthy subjects, and a steady protocol was applied to three of the subjects before and after short-term training. The peak blood velocity in the common carotid artery increased by 73.1% during the intermittent protocol and recovered to resting level within 3 minutes, while the heart rate (HR) remained high even 5 minutes after exercise. R wave amplitude (RWA) increased significantly from 1.40 +/- 0.39 mV at rest to 1.59 +/- 0.33 mV (P < .05) immediately after the start of walking, and decreased gradually to 1.46 +/- 0.36 mV (P < .05) during 3 minutes of walking. Thus, it decreased significantly to 1.31 +/- 0.40 mV (P < .01) during the interphase from exercise to rest, and increased again during recovery or rest periods in the intermittent protocol. The results suggest that an increase in the venous return per heart beat at the start of walking induces the increase in RWA, and that its abrupt decrease at the end of walking induces the decrease in RWA. Subjects with a higher HR response and recovery slopes have smaller abrupt changes in RWA at the interphases between rest and walking. The gradual decrease in RWA during walking may be related to a gradual increase in HR and a gradual decrease in systemic peripheral resistance, and the gradual increase in RWA after walking may be related to a gradual decrease in HR and a gradual increase in systemic peripheral resistance.

Increase of R-wave in pre-discharge ergometric test after myocardial infarction indicates advanced left ventricular injury, latent serious arrhythmias and worse prognosis

Changes in R-wave amplitude during exercise tests performed soon after myocardial infarction (15-31 days, mean 22) were analyzed in 78 men in relation to left ventricular injury (determined by 2-D echocardiography), ventricular arrhythmias (24-h Holter monitoring) and survival after myocardial infarction. It has been found that in patients with mild left ventricular injury (n = 51, Heger index < or = 3) the sum of the R-wave amplitude in 15 precordial leads recorded immediately after exercise decreased by 3.7 +/- 10% in comparison with resting values. In the patients with major left ventricular injury (n = 26, Heger Index > 3) the sum of R-wave amplitude after exercise increased by 12.9 +/- 17.5% (P < 0.001). Positive linear correlation (r = 0.35, P < 0.01) was observed between the level of left ventricular wall motion disturbances and R-wave amplitude changes. In patients with normal or slightly disturbed cardiac rhythm (n = 42, Lown scale 0-2) the sum of the R-wave amplitude after exercise decreased by 5 +/- 18% as compared to resting values, whereas in the patients with complex arrhythmias (n = 23, Lown scale 3-5) the sum of R-wave amplitude increased amounting to 9.9 +/- 17% (P < 0.001). Out of 17 patients who died during 5-year follow up, 16 displayed an increase or no change of the sum of R-wave amplitude. The same kind of relations between R-wave amplitude changes and left ventricular injury or cardiac arrhythmias were noted in patients with anterior and inferior myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the QRS segment during exercise: effects of acute beta-blockade with propranolol

Changes in the QRS complex during exercise may provide information with respect to ischaemic heart disease. The intention with present investigation was to shed light on mechanisms behind QRS changes and to study the possibly confounding effects of beta-blockade on such alterations with exercise. Placebo or propranolol respectively was infused in randomized and double-blinded order in seven young healthy men before a maximum exercise test. Advanced computerized vectorcardiography and impedance cardiography was recorded continuously together with blood pressures and blood samples. The Y-lead magnitude increased significantly with propranolol infusion (P < 0.05), but it tended to decrease in the Z-lead (P < 0.07). While the serum potassium concentrations increased (P < 0.0005), the spatial QRS magnitude tended to decrease irrespective of treatment (P < 0.07). These changes correlated with changes in QR-duration (adj r2 > 0.58). With exercise, the mean spatial QRS magnitude decreased with similar amounts irrespective of treatment. However, propranolol made the magnitude decrease earlier (P < 0.01). No effect of treatment was detected on the decrease in QRS-duration. Immediately after exercise, the QRS complex continued to change as during exercise in the placebo investigations, but did not with propranolol (P < 0.05). These different patterns were most obvious in the first half of the QRS complex in the Y-lead. It is concluded that acute beta-blockade modifies QRS alterations both during and after exercise in healthy subjects. This indicates that such drugs may have confounding effects in evaluations of the diagnostic value of QRS alterations.

Improved diagnostic performance on the severity of left ventricular hypertrophy with body surface mapping

To improve the diagnostic usefulness of electrocardiography (ECG) in determining the severity of left ventricular hypertrophy (LVH) with body surface mapping, 87 unipolar ECGs were recorded from 57 patients with left ventricular (LV) concentric hypertrophy and 30 with LV dilatation. Body surface ECG features due to LVH were evaluated by increase of QRS voltage and delayed local activation. We measured for each lead R voltage, net area of QRS (AQRS), ventricular activation time (VAT), and departure index (DI) of AQRS and VAT (DI = mean/SD). From these measurements, seven parameters were calculated for each patient: Rmax, the maximal R wave voltage; AQRSmax, the maximal AQRS; AQRS-Dmax, the maximal AQRS DI; AQRS-Darea, the area size where DIs of AQRS are more than 2; VATmax, the maximal VAT; VAT-Dmax, the maximal VAT DI; and VAT-Darea, the area size where DIs of VAT are more than 2. Among these parameters, the most effective for diagnosis of LVH were selected by stepwise multiple regression analysis. In the concentric hypertrophy group, the combination of VAT-Darea and Rmax was determined to be the best for estimating wall thickness. The regression equation determined from them correlated well to wall thickness (r = 0.73). In the LV dilatation hypertrophy group, only AQRSmax was selected for estimating LV dilatation. A good correlation between AQRSmax and LV internal dimension was observed (r = 0.73). With the body surface distribution of VAT prolongation, septal hypertrophy was separated from the other LVH. These were superior to the conventional method of 12-lead ECGs. ECG diagnosis of LVH severity improved by incorporating a mapping study. Also, prolongation of VAT and increase in QRS voltage were shown to be important when determining the severity of LVH.

R wave of the surface and intracoronary electrogram during acute coronary artery occlusion

Increases in electrocardiographic R-wave amplitude in humans have been described with positive and negative dynamic exercise test findings, episodes of variant angina and myocardial ischemia and infarction. The role of factors other than acute reversible ischemia in the genesis of these R-wave size alterations is unclear. To evaluate the contribution of acute ischemia to changes in R-wave size in the absence of other confounding variables, electrocardiograms were recorded before and during coronary angioplasty balloon inflation. The frontal leads and V1, V2, V5 and V6 were recorded during the last 10 seconds of coronary occlusion in 20 patients and intracoronary epicardial electrograms were recorded continuously during balloon inflation in 10 patients. Inflations were 8 +/- 2 atm for 52 +/- 36 seconds. Chest pain occurred in 26 of 30 patients with balloon inflation and ST elevation occurred in 22. No significant increases in R amplitude were noted in any lead or in the sum of the R waves in all leads, including intracoronary electrograms. In contrast, R amplitude tended to decrease. The initial decrease in both surface and epicardial R amplitude was similar to the first of the biphasic changes observed in animal models. An increase in R-wave amplitude is not by itself always a marker for myocardial ischemia, but depends on severity and duration of the process.

Electrocardiographic diagnosis of chamber enlargement

The purpose of this article is to review the changing role of the electrocardiogram in the diagnosis of cardiac chamber enlargement. Electrocardiographic criteria for the diagnosis of ventricular hypertrophy and atrial enlargement are reviewed in relation to autopsy, angiographic, echocardiographic and imaging findings. The electrocardiographic theory underlying the recognition of hypertropphy or dilation incorporates a number of sound physical principles that may lead to meaningful correlations with the tissue mass, chamber diameter and intracardiac blood volume. However, there are limiting factors related to the variable orientation of the heart in the chest, variable extracardiac factors and nonspecificity of each depolarization and repolarization abnormality used in the diagnosis of hypertrophy or dilation. This explains the superiority of the new noninvasive methods, in particular echocardiography, in the diagnosis of hypertrophy. Echocardiography is superior to electrocardiography in the detection of mild hypertrophy, and is more useful in the serial follow-up of changes during progression or regression of chamber enlargement.

Change in ventricular cavity size: differential effects on QRS and T wave amplitude

Although many factors have been reported to change the R wave amplitude of the electrocardiogram (ECG), few observations have been made of the associated changes in T wave amplitude. We hypothesized that changes in R and T wave amplitude should parallel each other. To test this hypothesis, R and T wave amplitudes were measured in 15 normal subjects during increased and decreased left ventricular dimensions induced by infusion of methoxamine and by Valsalva maneuver, respectively, as well as during changes in the proximity of the left ventricle to the chest wall (i.e., shift in patient position from supine to left lateral position). Simultaneous nine-lead ECGs and two-dimensional-guided M mode echocardiograms of the left ventricle were recorded at rest and under each experimental condition. R wave amplitude increased as the left ventricular lateral wall moved closer to the V5 and V6 electrodes. Alterations in R wave amplitude seen with changes in left ventricular chamber size were primarily caused by radial movement of the left ventricle in relation to the chest wall. Proximity of the left ventricle to the chest wall was therefore a major determinant of R wave amplitude. In contrast, T wave amplitude varied directly with alterations in left ventricular chamber size but was unaffected by changes in proximity to the recording electrode on the chest wall. Left ventricular chamber size, and possibly the associated alteration in endocardial-to-epicardial surface area ratio, appeared to be the major determinants of T wave amplitude.

Albumin-induced changes in the electrocardiographic QRS complex

The amplitude of the QRS wave of the electrocardiogram was correlated with conventional serum electrolyte concentrations in 94 nonhypertensive and 53 hypertensive patients. There was a highly significant correlation of QRS amplitude with serum albumin level in both groups. There was also significant correlation with serum calcium level in the nonhypertensive group, but this significance disappeared after correction for albumin. Changes in the serum albumin level during the hospital admission of the nonhypertensive patients were positively correlated with changes in QRS amplitude. Albumin infusion into 13 healthy persons resulted in significantly increased QRS amplitude, which was related to changes in serum albumin concentration. These results suggest that changes in serum protein concentration cause changes in QRS amplitude, possibly as a result of increased conductivity.

Relation of electrocardiographic R-wave amplitude to changes in left ventricular chamber size and position in normal subjects

Although exercise-induced changes in electrocardiographic R-wave amplitude have been ascribed to changes in left ventricular (LV) size, QRS axis, heart rate and ischemia, the physiologic mechanism remains unclear. To clarify the relation between R-wave amplitude and changes in LV size and position, simultaneous 9-lead electrocardiograms and targeted M-mode echocardiograms were recorded from 15 normal subjects. Recordings were made at rest, during Valsalva maneuver and during methoxamine infusion. LV diastolic dimension increased with methoxamine and decreased with Valsalva maneuver (p less than 0.001). R-wave amplitude in leads V5 and V6 varied directly with LV dimensions (p less than 0.001). The correlation coefficient between the change in R-wave amplitude in V5 or V6 and the change in LV dimension was 0.81 (p less than 0.01). No significant changes in R-wave amplitude were seen in electrocardiographic leads I, II, III, aVR, aVL, aVF or V1. Distance from the chest wall to the LV posterior wall correlated with change in R-wave amplitude (r = 0.79, p less than 0.001). Change from supine to left lateral position moved the left ventricle closer to the lateral chest wall in association with a 41 +/- 8% increase in R-wave amplitude in V5 and V6 (p less than 0.001). In conclusion, there is a direct and a dynamic relation between R-wave amplitude and LV chamber size. Chamber size and distance from the left ventricle to leads V5 or V6 interact as major determinants of R-wave amplitude.