Pacing Spikes All Over

Ventricular safety pacing (VSP) is used to avoid cross talk by delivering ventricular stimulus shortly after an atrial-paced event if ventricular-sensed event occurs. Although VSP is a protective feature that exists for decades in different pacing devices, there are some reports of unfavorable outcomes of this algorithm. More so, health care providers sometimes face difficulties in interpreting and dealing with VSP strips. This case report discusses an important pacemaker algorithm and encourages further attention to possible pitfalls and hence avoids unnecessary interventions

Predictors of mortality by Cox regression analysis.

<p>Predictors of mortality by Cox regression analysis.</p

Hazard ratio for clinical outcome according to QRS-T angle levels by Cox regression analysis.

<p>Hazard ratio for clinical outcome according to QRS-T angle levels by Cox regression analysis.</p

Relation between QRS-T angle and left ventricular systolic function.

<p><b>(A)</b> Scatter plot demonstrating an inverse linear relation between QRS-T angle and left ventricular ejection fraction. Linear regression: R² = 0.103, B = -1.06, Standard error 0.11, P<0.0001. <b>(B)</b> Box plot of the median QRS-T angle stratified according to the left ventricular ejection fraction. Median QRS-T angle was wider with reduction in left ventricular ejection fraction (Kruskal Wallis test; P<0.001). Box plots denote median and inter-quartile range (IQR); whiskers are of maximum 1.5 IQR.</p

Changes in the QRS-T angle.

<p>Histogram of the QRS-T angle difference in degrees between baseline and follow-up ECG. The continuous line denotes the normal distribution curve.</p

Kaplan Meier survival analysis according to baseline QRS-T angle category stratified by gender.

<p>The tertile QRS-T angle percentiles were 40° and 103° in women and 51° and 125° in men. The estimated cumulative survival rate at the median follow-up time was reduced with increasing baseline QRS-T angle category; 67.9±1.5% vs. 61.2±1.5% vs. 52.1±1.6%, P<0.001.</p

Hazard ratio for mortality according to the difference in QRS-T angle between follow-up and baseline ECG by Cox regression analysis.

<p>Hazard ratio for mortality according to the difference in QRS-T angle between follow-up and baseline ECG by Cox regression analysis.</p

Widening of the QRS-T angle on follow-up was associated with increased mortality.

<p><b>(A)</b> Kaplan Meier survival analysis according to QRS-T angle change calculated by the difference between follow-up and baseline ECG. An increase in the QRS-T angle on follow-up above 30° was associated with an increased mortality. The estimated cumulative survival rate at the median follow-up time of 342 days was reduced with an increased QRS-T angle difference; 61.9±1.5% vs 63.6±1.9% vs. 53.3±2.0%, Log rank P<0.00001. <b>(B)</b> Cox regression analysis with adjusted hazard ratio for mortality (with 95% confidence interval) of the QRS-T angle change as a continuous variable using restricted cubic splines with 3 knots at the 5^th, 50^th and 95^th percentiles of the QRS-T angle change distribution, P<0.0001. Parameters included were parameters outlined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194520#pone.0194520.t003" target="_blank">Table 3</a> with the addition of baseline QRST-T angle.</p