Normally    when    blood    supply    to    a    portion    of    the    heart    muscle    is    inadequate    (ischaemia)    you    will    suffer    from    angina characterised by one of the following - • acute chest pain, • feeling tight in your chest or • pain radiating to your left arm, shoulder or neck. If   the   blood   supply   is   cut   off   completely   you   will   suffer   a   heart   attack.   These   symptoms are well known to most of us and we will seek urgent medical help if it occurs.  However,    there    are    many    in    the    world    who    suffer    from    ischemic    episodes    without realising   it   as   they   do   not   have   symptoms   normally   attributed   to   angina.   This   is   known as   silent   ischaemia.   They   may   also   suffer   a   heart   attack   with   no   warning.   People   who have    had    previous    heart    attacks    or    those    with    diabetes    are    especially    at    risk    of developing   silent   ischemia.   It   is   said   that   "silent"   (asymptomatic)   myocardial   ischemia   is the   most   common   manifestation   of   coronary   heart   disease   (CHD),   accounting   for   more than 75 percent of ischemic episodes during life. Painless   myocardial   infarctions   on   the   other   hand   vary   a   little   from   silent   ischaemia   or   infarction.      Although   there   may   not   be chest   pain   or   radiating   pain   in   painless   myocardial   infraction,   other   symptoms   relating   to   the   condition   may   be   present.   They are: • Profuse sweating • Palpitation (due to increased sympathetic activity) • Breathlessness (due to cardiac failure)  • Feel faint (syncope due to hypotension) • Extreme fatigue (due to poor tissue perfusion) • Sometimes patients become unconscious because of severe cerebral hypoperfusion (not enough blood reaching the brain). Both   silent   ischaemia   and   painless   ischaemia   occur   in   poorly   controlled   diabetics   and   non-diabetics   over   the   age   of   seventy. The   reason   is   because   the   pain   conducting   nerve   fibres   are   paralysed   in   diabetes   and   old   age   and   hence   you   do   not   feel   the pain. If   any   of   the   symptoms   described   above   is   seen,   it   is   essential   to   have   your   heart   checked   urgently.   Diabetics   must   be particularly warned about this.  Investigations: • Urgent ECG will normally show changes relating to ischaemia or infarction. • Blood Test to check cardiac enzymes and proteins should be done even when the ECG appears normal.   The   blood   test   will   measure   the   levels   of   enzymes   and   proteins   that   are   linked   with   injury   of   the   heart   muscle.   They   include the   enzyme   creatine   kinase   (CK),   and   the   proteins   troponin   I   (TnI)   and   troponin   T   (TnT).   Their   levels   will   rise   if   the   heart   has suffered an injury.  If the ECG and blood tests are inconclusive two further tests could be done to make sure your heart is healthy. Ambulatory Electrocardiogram: • I f   your   doctor   is   able   to   arrange   this,   a   small   recorder   will   be   attached   by   a belt   to   your   waist.   The   machine   will   be   connected   by   wires   to   your   chest.   It will   continuously   record   the   electrical   activity   of   your   heart   as   you   carry   on with   your   normal   activities   over   a   period   of   24   to   48   hours.   If   your   heart   is affected   during   this   period   your   doctor   will   be   able   to   pick   this   up   through the recording on the machine. Stress ECG : • This   will   be   the   ultimate   test   to check    if    your    heart    is    normal and   healthy.   Here   you   will   be   connected   to   the   machine   by   a   few   leads.   The ECG   is   then   recorded   while   you   are   on   a   treadmill.   The   stress   levels   of   your heart   will   be   increased   slowly   by   making   you   walk   faster   and   if   necessary with the treadmill at an upward incline. • This   test   should   only   be   done   with   a   cardiologist   nearby   as   he   will   know when   to   stop   the   test   if   you   are   in   trouble   or   will   be   able   to   resuscitate   you immediately if you suffer from a cardiac episode. Complication   and   mortality   are   more   often   seen   in   painless   infarction   than   when   you   have   associated   chest   pain.   The probable   cause   for   high   mortality   is   that   patients   normally   ignore   their   symptoms   when   they   have   no   chest   pain.   They   usually continue   with   their   routine   activities,   if   symptoms   are   bearable.   Continued   activity   in   the   presence   of   myocardial   infraction will   lead   to   complications like   irregular   heart   beat,   cardiac   failure   and   death.   This   is   very   common   in   India   compared   to   other countries. It is estimated that more than 900 Indians under the age of 30 die from it everyday. It   is   more   difficult   to   identify   someone   with   silent   ischemia   or   infarction   as   they   do   not   have   any   symptoms   recognised   as originating   from   the   heart.   High   risk   populations   (diabetics   and   elderly)   should   be   made   aware   of   this   and   should   be   advised on regular health checks and how they should protect their heart.    It   is   important   that   everyone   becomes   aware   of   this   silent   killer.   If   you   have   had   any   of   the   symptoms   mentioned   with   no accompanied chest pain, do not assume that your heart is not the cause. Seek advice and have your heart checked.   Prof. S. Vaithinathan, MD., DM Cardiology.