"It was just going fast, it wasn't irregular," Jansen said after joining teammates for the end of workouts. "I just didn't want that feeling again from last year so we double-checked because of my history. It's nothing big. We don't know what caused it, but I'm OK."
Jansen, who pitched one perfect inning of relief in his spring debut Wednesday, said he plans to make his next scheduled game appearance Saturday. He was not prescribed any new medication, medical procedures or scheduled for further tests.
Dodgers manager Don Mattingly wasn't sure if Jansen's timetable would hold up.
"As long as Sue [Falsone, head trainer] says he's all right," Mattingly said about Jansen pitching on Saturday. "Kenley's not coming in here and telling us what to do. We're going to go with the science."
Falsone seemed to support Jansen's opinion, although she said doctors weren't sure what caused Jansen's discomfort other than to rule out another arrhythmia.
"He should be fine," she said. "If nobody is worried, he'll be OK to throw tomorrow."
Jansen, who set an MLB record last year for strikeouts per nine innings, was hospitalized last July with an irregular heartbeat and had to be disabled for three weeks because he was prescribed a blood thinner and couldn't participate in competitive activity.
The Dodgers said Jansen experienced similar "flutters" Thursday night and shortness of breath. He reported to Camelback Ranch-Glendale Friday morning and was taken to the local internist.
Mattingly said he hadn't heard of Jansen experiencing any problems since last year's incident and added that Jansen is already on blood pressure medication and "not supposed to take any caffeine."
"This is the first I've heard of it since the issue last year," he said.
At that time, Jansen underwent a cardio conversion to get rhythm back to his heartbeat by shocking it with electrodes.
Jansen set a Major League record last season striking out a staggering 16.1 batters per nine innings (with a minimum of 50 innings). Jansen fanned 96 in 53 2/3 innings, raising the bar from the 15.99 mark set by Cubs closer Carlos Marmol last year.
Despite an erratic early season that led to a brief Minor League demotion and another stint on the disabled list with a sore shoulder, he had a splashy 2.85 ERA at the finish underscoring an in-season transformation almost as remarkable as the one he made two years ago when he went from catcher to pitcher.
In his last 31 2/3 innings, Jansen allowed only nine hits in 102 at-bats (.088) and saved five of six opportunities on the season. In September, Jansen struck out 32 and walked only three.
Jansen, 24, leaped over some pretty impressive Dodgers relievers as a one-season strikeout machine, closers like Cy Young winner Eric Gagne (14.98) and All-Stars Jonathan Broxton (13.50) and Takashi Saito (12.29).
Jansen, a native of Curacao and Little League teammate of Atlanta's Jair Jurrjens, gained notoriety for throwing out basestealers from his knees during the World Baseball Classic two years ago but was converted from a weak-hitting catcher to the mound during that 2009 season.
He opened the 2010 season in Class A and ended it closing games in the Major Leagues, dominating at Double-A Chattanooga in between and saving the Double-A All-Star Game. He earned a save in his second Major League appearance and four saves in 25 games. Jansen struck out 41 with 15 walks in 27 innings and his 0.67 ERA was the fourth lowest by a rookie with a minimum of 25 innings in Major League history.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.