Relationship of QRS amplitude to left ventricular dimensions after acute blood volume reduction in normal subjects

Changes in R-Wave amplitude in DII lead is less sensitive than pulse pressure variation to detect changes in stroke volume after fluid challenge in ICU patients postoperatively to cardiac surgery

OBJECTIVE

The amplitude of R-wave in DII lead (RDII) has been shown to correlate to central blood volume in animal and healthy volunteers. The aim of this study was to assess if change in RDII (DeltaRDII) after passive leg rise (PLR) and fluid loading would allow detecting preload dependence in intensive care ventilated patients. This parameter was compared to concomitant changes in pulse arterial pressure (DeltaPP).

METHODS

Observational study in 40 stable sedated and ventilated cardiac surgery patients studied postoperatively. In line with our routine practice we performed a 45 degrees passive leg rise (PLR1) to detect preload dependence. If cardiac index or DeltaPP rose more than 12 and 13%, respectively, the patient was declared as non-responder (NR) to fluid loading. If these criteria were not met, they were declared as responders (R) and received a 500 ml of gelatin fluid loading (FL) followed by a second passive leg rise (PLR2). Hemodynamic parameters were assessed during each maneuver using their indwelling Swan-Ganz and radial catheter.

RESULTS

We identified 16 R and 24 NR whose hemodynamic parameters did not differ at basal condition, except DeltaPP (19% +/- 7 in R vs. 7% +/- 4 in NR, P < 0.001). PLR1 did not elicit any hemodynamic change in NR. In R, DeltaPP decreased and SV rose, both significantly (P < 0.001) whereas DeltaRDII did not vary. FL induced a more pronounced change in these parameters.

CONCLUSIONS

DeltaRDII in response to PLR does not successfully help identifying preload dependent patients contrarily to DeltaPP or change in stroke volume.

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.

Association between R-wave amplitude of the electrocardiogram and myocardial function during coronary artery bypass grafting

OBJECTIVE

The recovery of R-wave amplitude in the V5 lead of the electrocardiogram (ECG) was recently found to be worse in nonsurvivors than in survivors after coronary artery bypass grafting (CABG). On the contrary, an increase in R-wave amplitude has been found to reflect myocardial dysfunction in exercise testing. The purpose of this study was to examine whether the changes in R-wave amplitude are associated with changes of myocardial function during CABG.

DESIGN

A prospective clinical study.

SETTING

Cardiothoracic division of surgery in a university hospital.

PARTICIPANTS

Ten consecutive patients undergoing CABG.

MEASUREMENTS

R-wave amplitude was measured at eight different time points. Left ventricular end-systolic wall tension, wall stress at isovolumic contraction (afterload), end-diastolic wall stress (preload), end-systolic wall stress per end-systolic area (contractility), and stroke work were calculated using transesophageal echocardiography and arterial pressure.

MAIN RESULTS

Linear regression was calculated between changes in R-wave amplitude and echo parameters. A weak positive association within subjects was noted among R amplitude and all measured cardiac function parameters except preload. R2 value varied from 0.101 to 0.266, and R2 for preload was 0.017.

CONCLUSIONS

These results suggest that only 10% to 27% of variation in R-wave amplitude can be explained by left ventricular function indices measured by echocardiography in patients with CABG. Thus, R-wave amplitude changes in an individual patient undergoing CABg have very limited utility as a noninvasive measure of left ventricular function.

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.