Found an article on said Krone newspaper, with a couple of pictures also:
Rekordversuch im Freitauchen endet dramatisch - Mann in Lebensgefahr - Österreich - krone.at
One or two errors, but no mention of cardiac arrest, perhaps removed.
Google translation + a little editing (not that I'm fluent in German):
Head:
Freediving record attempt ends dramatically
Bi:
Months of planning, six weeks of intensive training - and after 4:30 minutes to 244 meters depth [800ft], a new world record. But off the coast of the picturesque Greek paradise island of Santorini, was the scene of a drama Wednesday afternoon for the Viennese extreme-diver Herbert Nitsch in the depths of the Mediterranean Sea.
Main:
The "crown" was nearly there in the daring venture, but the world record attempt took a dramatic turn: As planned, the 42 year old re-appeared after exactly 4'23" minutes. He was immediately supplied with oxygen and then placed under the surface, where his lungs - after having been squashed by the immense pressure to the size of an orange - should unfold again. (Others) anxiously wait on the surface.
After a good 20 minutes the extreme athlete appeared again. But he struggled to breathe, and instinctively grabbed his throat. Within seconds, Nitsch was hoisted onto a motor boat and taken ashore, but was still conscious.
(Bi) Father watches at the bedside
"He's fine," was the first announcement from his crew, as "purely a safety measure" the diver was flown to a decompression chamber in Athens. A little later, this was stated from the hospital: "The patient was intubated, his condition is critical." Father Gerhard monitored him at the bedside.
That the ambitious project was successful for Nitsch moves to the background. He was still wearing the measuring device on the wrist as he was flown to the Greek capital - the depth gauge stood at 800 feet [244m].
The project "Extreme 800" was planned to the smallest detail. Only to be knocked down at the last moment. Strong westerly winds and turbulent waters had forced Nitsch to change location. The new scene of world-record attempt was in the Bay of Thirassia, a small volcanic island near Santorini. At 2 p.m. Viennese time he got into the water, 30 minutes later he re-emerged. The accompanying boats reigned in tense silence. At emergence, there was applause at first, then tragedy took its course ...
(Bi) Dive physicians were skeptical
Even in advance the doctors took to their heads on the proposed project: "Just don't," warned many doctors the 42 year old, the risk was too great. Diving expert Dr. Roswitha Prohaska: "Medicine does not know what happens at these depths, there are already too many accidents happening, too many questions unanswered."
(Bi) Facts and Records
Freediving, also known as breath hold diving, is considered the earliest form of diving. In contrast to scuba diving only one deep breath is taken. This type of breath holding is referred to as "apnea". Already in the stone age this was pursued. In recent decades, free diving has become an extreme sport. Various competitions around the globe set the world's best against each other.
The royal discipline is "No Limits": The athlete is attached on a sled or lift and is pulled into the depths. The world record currently stands at 217 meters [error: 214]. In "Free Immersion" is not allowed any use of diving fins or other aids. For propulsion, he pulls on a rope into the deep and back up. Record: 120 meters.
In "Constant Weight with Fins" the diver plunges without technical tools, but with fins. The record here is at 124 meters, set in 2009 in the Bahamas. Another important discipline is called "Variable Weight". The athlete is pulled into the depths, but must get back to the surface again on their own accord. The world record here is 142 meters.
Oliver Papacek and Christian Pichler, Kronen Zeitung/edit.