Our heart has 4 chambers. The lower left one is called left ventricle (please read my website www.thefitheart.in for further details). When  ECG shows increased left ventricular electrical forces, then we say that there is left ventricular preponderance, which simply means that the left ventricle has grown in size (for which there are multiple causes). But your father's blackouts need detailed evaluation as it could be dangerous. So please meet a cardiologist as early as possible and get him properly examined to plan the further line of management. Thanks. Hope this helps. Dr Chandrashekhar Munjewar, Mumbai www.thefitheart.in