The short term influence of right ventricular pacing burden on echocardiographic and spiroergometric parameters in patients with preserved left ventricular ejection fraction oleh Akram Youssef, Christian Pfluecke, Maciej Dawid, Karim Ibrahim, Michael Günther, Steffen Kolschmann, Utz Richter, Alexander Francke, Carsten Wunderlich, Marian Christoph