Traditionally, heart rate (HR) deceleration, is used as a measure of attention to media. Though HR is under the dual control of the parasympathetic (PNS) and sympathetic nervous systems (SNS), research suggests that, in the TV viewing context, parasympathetic responses dominate the HR. Research assessing the impact of arousing content and pacing—both of which are thought to increase both PNS and SNS activation—has interpreted HR as an indicator of PNS. This study seeks to determine if the use of heart rate variability (HRV) indices which are designed to separately assess the contributions of PNS and SNS activation to changes in HR, can be used to tease out the SNS and PNS responses to mediated messages. To date HRV metrics have rarely been used in media research. Within the framework of limited capacity model of motivated message process (LC4MP) an experiment was performed measuring self-reported and physiological responses to television messages with varying arousing content, pacing and valence. Traditional HR analysis replicated the previous empirical findings and supported the theoretical predictions. However, the expectation that the HRV indices would add to our knowledge of media processing was not met. Rather the HRV results were incongruent with both the traditional analysis and theory. It is suggested that this may be because HRV is computed over the entire message and is summative in nature and therefore does not provide a measure of moment to moment change in PNS or SNS activation during message processing. It is recommended that research be undertaken to determine if computing the metrics on shorter contiguous periods during media viewing would provide information on intra-message processing.