(plaintiff was working for defendant when he became ill; after driving defendant’s tractor back to farm, he went home and was taken to the hospital where it was determined he had a heart attack and his heart was damaged; plaintiff sued his employer and claimed entitlement to bring civil action for failing to secure workers compensation benefits and negligence; defendant moved for summary judgment and plaintiff sought to amend petition to allege negligence in failing to secure workers compensation as required by statute; trial court granted summary judgment and denied leave to amend petition; on appeal, court held workers compensation claim could not be decided in district court as exclusive jurisdiction resided with workers compensation; sole remedy for failing to have workers compensation is employee’s ability to bring negligence claim; court also held no negligence existed because plaintiff’s heart attack was not foreseeable when he merely mentioned to defendants he did not feel well, so no duty existed to render aid; court also upheld denial of motion to amend because it was untimely and futile).