Demonstration of the relationship between heart dimensions and QRS voltage amplitude

Isolated very low QRS voltage predicts response to tilt-table testing in patients with neurally mediated syncope

BACKGROUND

A number of patients with neurally mediated syncope (NMS) have isolated QRS complexes of very low voltage (≤0.3 mV) in the frontal plane leads on the 12-lead electrocardiogram (ECG).

HYPOTHESIS

The aim of this study was to assess the importance of QRS voltage in predicting response to tilt-table testing (TTT) in patients with suspected NMS.

METHODS

We included 216 patients (age: 49 ± 20 years, 103 men) with suspected NMS who had either a positive or negative response to TTT (n = 91 TTT+, and n = 125 TTT-). The QRS voltage was measured in mV on 12-lead ECGs performed within 3 days of the TTT. The lowest QRS voltage (QRSmin), as well as the voltage in each of the 12 leads was also determined.

RESULTS

Very low voltage (QRSmin  ≤ 0.3 mV) in the frontal leads was significantly more prevalent in the TTT+ group than in the TTT- group (74 vs 22%, respectively; P  < .001). Patients in the TTT+ group had significantly lower QRSmin when compared to patients in the TTT- group. QRSmin predicted a positive tilt-table test in a multivariate model that also included patient gender, height, history of presyncope, QRS duration, and left ventricular end-diastolic diameter indexed to height. ROC analysis showed that QRSmin of ≥0.3 mV discriminated between TTT+ and TTT- patients with a sensitivity of 78% and specificity of 68%.

CONCLUSION

Isolated very low QRS voltage in the frontal leads predicts a positive response to TTT in patients with suspected NMS.

Isolated very low QRS voltage in the frontal leads predicts recurrence of neurally mediated syncope

BACKGROUND

The study was prompted by our observation that some patients with neurally mediated syncope (NMS) have an isolated QRS complex, of very low voltage (≤0.3 mV cutoff), in 1 of the frontal leads on the 12-lead electrocardiogram.

OBJECTIVE

To prospectively evaluate whether the presence of isolated very low voltage (VLV) predicts recurrence of NMS.

METHODS

We included 205 patients (aged 50 ± 17 years) with a median of 3 syncopal episodes. Tilt testing was performed in all patients and was positive in 87 (42%). The patients were followed for a median of 14 months.

RESULTS

VLV in frontal leads was present in 92 patients (45%). During the follow-up period 60 patients experienced recurrence of syncope. The actuarial total syncope recurrence rate at 1 year was 32% (95% confidence interval [CI 23%-44%) in patients with isolated VLV in frontal plane leads, and 14% (95% CI 8%-24%) in patients without VLV (log-rank test P < .0001). The significant relationship between the presence of isolated VLV in the frontal leads and syncope recurrence was retained in Cox multivariate analysis that included the history of presyncope and syncope as well as the left ventricular end-diastolic diameter. The presence of isolated VLV in frontal leads was associated with a 3-fold increase of the risk of recurrent syncope.

CONCLUSIONS

Isolated very low QRS voltage in the frontal leads predicts recurrence of NMS independent of clinical factors that predict recurrence of syncope in such patients. This phenomenon may help generate new diagnostic tools and insights into the pathogenesis of NMS.

Sokolow-Lyon voltage is suitable for monitoring improvement in cardiac function and prognosis of patients with idiopathic dilated cardiomyopathy

BACKGROUND

The clinical significance of electrocardiogram in the assessment of patients with idiopathic dilated cardiomyopathy (IDCM) is currently unknown. The aim of this study was to determine the feasibility of recording serial changes in Sokolow-Lyon voltage (∆%QRS-voltage) in one year to estimate left ventricular reverse remodeling (LVRR) and predict a prognosis of IDCM patients under tailored medical therapy.

METHODS

Sixty-eight consecutive patients with mild symptoms (52.1 ± 13 years old; 69% men; NYHA I/II/III/IV; 33/29/6/0) underwent electrocardiography and echocardiography at baseline and 12 month follow-up (follow-up period: 3.9 years).

RESULTS

LVRR was observed in 30 patients (44.1%). The ∆%QRS-voltage was significantly lower in the LVRR group (LVRR; -26.9%, non-LVRR: -9.2%, p < .001). Univariate analysis showed that ∆%QRS-voltage correlated with ∆%LV end-diastolic diameter (r = .634, p < .001), and with ∆%LV ejection fraction and ∆%LV mass index (r = -.412, p < .001; r = .429, p < .001 respectively). Using receiver operating characteristic curve analysis for the estimation of LVRR, ∆%QRS of -14.7% showed optimal sensitivity (63.2%) and specificity (83.3%) (AUC = 0.775, p < .001). The composite endpoints of cardiac death (n = 0), hospitalization for advanced heart failure (n = 11) and fatal arrhythmia (n = 2) were observed in 13 patients during the follow-up period. Kaplan-Meier analysis showed significantly higher event-free rate in patients of the low ∆%QRS-voltage group (<-14.7%) (83%) than those of the high group (66%, p = .022).

CONCLUSIONS

The present study showed that decrease in Sokolow-Lyon voltage is associated with improvement in cardiac function and favorable prognosis in IDCM patients on medical therapy, suggesting that this index is a feasible marker for response to treatment of IDCM.

Risk of mortality in individuals with low QRS voltage and free of cardiovascular disease

The prognostic significance of low QRS voltage (LQRSV) in the electrocardiogram (ECG) of individuals free of cardiovascular disease (CVD) is unclear. We evaluated the association between LQRSV and all-cause mortality in 6,440 participants (53% women, mean age 60 years) from the Third National Health and Nutrition Examination Survey, a representative sample of the US population. Participants with history of CVD or major ECG abnormalities were excluded. LQRSV was automatically defined from standard 12-lead ECG as QRS complex amplitudes of <0.5 mV in all frontal leads and/or <1.0 mV in all precordial leads. Mortality data through 2006 were obtained from National Death Index records. LQRSV was detected in 1.4% (n = 89) of the participants. During a median follow-up of 13.8 years, 2,000 deaths occurred. The mortality rate in individuals with LQRSV was almost twice that in those without LQRSV (51.1 vs 23.5 events per 1,000 person-years, p <0.01). In a demographic-adjusted model, LQRSV was associated with 63% increased risk of mortality (hazard ratio 1.63, 95% confidence interval [1.21, 2.18]). The magnitude of this risk did not appreciably change after additional adjustment for body mass index, smoking status, systolic blood pressure, blood pressure medication use, dyslipidemia, diabetes, cancer, pulmonary disease, and ECG abnormalities (hazard ratio 1.61, 95% confidence interval [1.20, 2.16]) and was consistent across age, race, and sex subcategories. In conclusion, LQRSV is associated with an increased risk of mortality in individuals free of apparent CVD. More research is warranted to determine the mechanisms by which LQRSV is associated with increased risk of mortality in apparently healthy individuals.

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.

Vectorcardiographic changes during laparoscopic cholecystectomy may mimic signs of myocardial ischaemia

BACKGROUND

Laparoscopic surgery involves the use of intra-abdominal carbon dioxide insufflation (pneumoperitoneum). The increased intra-abdominal pressure causes marked haemodynamic changes, which may influence electrocardiographic monitoring. The aim of the present study was to elucidate the influence of pneumoperitoneum on vectorcardiographic recordings.

METHODS

Vectorcardiographic changes (QRS vector difference = QRS-VD, QRS loop area, QRS magnitude, ST vector magnitude, spatial ST vector change) were recorded continuously applying computerized vectorcardiography in 12 anaesthetised cardiovascularly healthy patients, scheduled for laparoscopic cholecystectomy. Measurements were made before and during pneumoperitoneum in three different body positions (supine, Trendelenburg and reversed Trendelenburg), also employing transesophageal echocardiography and invasive blood pressure monitoring.

RESULTS

Pneumoperitoneum significantly increased QRS-VD, in parallel with an enlargement in loop area and magnitude. The magnitude was significantly increased in the transversal and frontal planes and there was a tendency to increase the magnitude in the sagittal plane. The increase in QRS-VD reached levels previously associated with the development of myocardial ischaemia in patients with coronary artery disease. The ST-variables were not changed by the pneumoperitoneum. The positional changes also influenced QRS-VD significantly.

CONCLUSIONS

When computerized vectorcardiography is used for ischaemia monitoring during pneumoperitoneum, the ST-variables seem reliable. However, vectorcardiographic QRS-changes should be interpreted with caution, as the QRS alterations found during pneumoperitoneum mimic the changes seen during myocardial ischaemia.