ecgviewer: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/ecgviewer - from package: pixelmed-apps

You may install the required package with command apt-get install {package}

Error in other languages:
ecgviewer: bevel nie gevind nie
ecgviewer: comandă negăsită
ecgviewer: comando não encontrado
ecgviewer: commande introuvable
ecgviewer: command not found
ecgviewer: käsku ei ole
ecgviewer: không tìm thấy lệnh
ecgviewer: komanda nerasta
ecgviewer: Kommando nicht gefunden.
ecgviewer: kommandot finns inte
ecgviewer: komut yok
ecgviewer: nie znaleziono polecenia
ecgviewer: níor aimsíodh an t-ordú
ecgviewer: no se encontró la orden
ecgviewer: no s'ha trobat l'ordre
ecgviewer: opdracht niet gevonden
ecgviewer: parancs nem található
ecgviewer: perintah tidak ditemukan
ecgviewer: príkaz nenájdený
ecgviewer: příkaz nenalezen
ecgviewer: команда не найдена
ecgviewer: командата не е открита
ecgviewer: 命令找不到
ecgviewer: コマンドが見つかりません